The correct answer is Bone-marrow.

Key Points

Red blood cell:

• Red blood cells (RBCs) are the most common type of blood cell and the vertebrate's principal means of delivering oxygen to the body tissues via blood flow through the circulatory system.
• RBC is formed in Bone Marrow.
• RBCs take up oxygen in the lungs, or in fish the gills, and release it into tissues while squeezing through the body's capillaries.
• The cytoplasm of erythrocytes is rich in hemoglobin, an iron-containing biomolecule that can bind oxygen and is responsible for the red color of the cells and the blood.
• Each human red blood cell contains approximately 270 million of these hemoglobin molecules.
• The cell membrane is composed of proteins and lipids, and this structure provides properties essential for physiological cell function such as deformability and stability while traversing the circulatory system and specifically the capillary network.

Additional Information

• Red blood cells are thus much more common than the other blood particles: there are about 4,000–11,000 white blood cells and about 150,000 - 400,000 platelets per microliter.
• Human red blood cells take on average 60 seconds to complete one cycle of circulation.
• The blood's red color is due to the spectral properties of the hemic iron ions in hemoglobin.
• Each hemoglobin molecule carries four heme groups; hemoglobin constitutes about a third of the total cell volume.
• The normal pH range of blood is between 7.35 to 7.45. This means that blood is naturally slightly alkaline or basic.

Hypertext transfer protocol (HTTP):

• HTTP is used to access data on the world wide web. HTTP functions as a combination of FTP and SMTP. HTTP uses the services of TCP port number 80. HTTP is a stateless protocol.
• HTTP prior to version 1.1 specified a non-persistent connection, while a persistent connection is a default.
• In a non-persistent connection, one TCP connection is made for each request/ response. The client opens a TCP connection and sends a request and server sends the response then closes the connection.

File Transfer Protocol (FTP):

• FTP stands for file transfer protocol. It is provided by TCP/IP for copying a file from one host to another. FTP can transfer a file through one of the following three modes: stream mode, block mode and compressed mode. Stream mode is the default mode.
• FTP uses two TCP connections one for data and another for control.

Simple Transfer Protocol (SMTP):

• SMTP is a push protocol, it can push the messages from the client to the server only.
• SMTP uses one TCP connection at a time

TELNET:

• TELNET is a client/ server application that allows a user to log on to a remote machine, giving the user access to the remote system.
• TELNET uses one TCP connection at a time.

Important Point:

Option 1 is not correct since HTTP might have more than one TCP connections for a single web page.

Explanation:-

Critical section:- A Critical section is a program segment where shared resources are accessed. Only when a process is in its critical section can it be in a position to disrupt other processes. We can avoid race conditions by making sure that no two processes enter their critical sections at the same time.

Here is the diagram of the critical section program as follows:

do{

entry section

       critical section

exit section

       remainder section

} while (true);   
 Important Points

• A minimum of variables are required to be shared between processes to solve the critical section problem.
• If a process is executing in its critical section, then no other processes can be executed in its critical section.

Additional InformationDeadlock:- A deadlock is a situation in which two computer programs sharing the same resource are effectively preventing each other from accessing the resources, resulting in both programs ceasing to function.

Semaphores in the operating system:- semaphores are integer variables that are used to solve the critical section problem by using two atomic operations, wait and signal that is used for process synchronization. 

The correct answer is A-I, B-II, C-III, D-IV.

Key Points

• Degana :
  • India's Rajasthan is home to the Degana Tungsten Deposit.
  • In 1915, the location was first identified.
  • This location's mineralization dates back to the Neoproterozoic period between 1.00 and 0.54 billion years ago.
  • Deposits of wolfram (wolframite) can be found in Renwat Hill in Degana.
  • In this mineral the tungstate of iron and manganese occurs, in the veins and lodes of granite and philites.
• Mando-ki-pal:
  • The 'Mando ki Pal' area of ​​Dungarpur in Rajasthan is famous for the flospar mineral.
• Jhamar Kotra:
  • The greatest phosphate reserve in India is located at Jhamar Kotra mines, which are located in southern Rajasthan near the Aravali mountain range.
• Goth-Manglod:
  • This area in Rajasthan is famous for gypsum.

The correct answer is Thermal power​.

• Thermal power is the main source of energy in Rajasthan.

Key Points

• Thermal power constitutes of 57.25% of the total power source of Rajasthan.
• Thermal Energy:
  • The energy which is produced when a rise in temperature causes atoms and molecules to move faster and collide with each other is called thermal energy.

Additional Information

• Wind energy plants in India are Muppandal Wind Farm, Tamil Nadu; Jaisalmer Wind Park, Rajasthan; Brahmanvel Wind Farm, Maharashtra.
• Nuclear Power Stations in India ar Tarapur Maharashtra; Kalpakkam Tamil Nadu; Narora U. P.; Rawatbhata Kota, Rajasthan; Kaiga Karnataka; Kakrapar Gujarat; Kudankulam Tamil Nadu.
• Hydroelectric plants in India are Tehri Hydropower Complex, Uttarakhand; Koyna Hydroelectric Project, Maharashtra; Srisailam Dam, Andhra Pradesh.
• Rajasthan:
  • Governor: Kalraj Mishra
  • Chief Minister:Ashok Gehlot

The correct answer is Tooth Enamel.

Key Points

• Tooth Enamel is the hardest substance in the human body.
• Tooth enamel is made up of crystalline Calcium Phosphate.
• Tooth enamel is the hard outer surface of the tooth that protects it from tooth decay.
• It is the hardest substance in the human body.
• However, it can corrode and develop cavities by the action of acids and substances released upon decomposition of the organic materials which are left, if the mouth is not kept clean properly.

Additional Information

• Skull Bones:​
  • The skull is made up of 29 bones.
  • The only bone that can move is Mandible.
  • The nasal bone is part of Skullbone.