The correct answer is Curvature of the lens.

Important Points

• Focal length of a lens depends on its curvature and the medium outside the lens.

Additional Information

• The ability of a lens to converge or diverge light rays depends on its focal length.
  • For example, a convex lens of short focal length bends the light rays through large angles, by focussing them closer to the optical centre.
  • Similarly, the concave lens of a very short focal length causes a higher divergence than the one with a longer focal length.
• The degree of convergence or divergence of light rays achieved by a lens is expressed in terms of its power.
  • The power of a lens is defined as the reciprocal of its focal length.

Given that Mars, Planets, Celestial Bodies.

All Mars situated in Planets and all Planets are situated in Celestial Bodies.

The Venn diagram given bellow-

Hence, option 1 is the correct answer.

The correct answer is Kwashiorkor.

Key Points

• Kwashiorkor disease of caused by protein deficiency.
• Kwashiorkor, also known as “edematous malnutrition” because of its association with edema (fluid retention), is a nutritional disorder most often seen in regions experiencing famine.
• It is a form of malnutrition caused by a lack of protein in the diet. People who have kwashiorkor typically have an extremely emaciated appearance in all body parts except their ankles, feet, and belly, which swell with fluid.

Important Points

• Most people who are affected by kwashiorkor recover fully if they are treated early.
• Treatment involves introducing extra calories and protein into the diet. Children who develop kwashiorkor may not grow or develop properly and may remain stunted for the rest of their lives.
• There can be serious complications when treatment is delayed, including coma, shock, and permanent mental and physical disabilities. Kwashiorkor can be life-threatening if it’s left untreated.
• It can cause major organ failure and eventually death.

Additional Information

Anuj ranks 23rd from the top → Students below Anuj are 73 - 23 = 50

Now the rank of Anuj from the below is 50 + 1 = 51th

Hence, Option (4) is correct.

Important Points

Position of the person from upward = [Total no. of persons - position of person from down] + 1

Position of the person from downward = [Total no. of persons - position of person from upward] + 1

The correct answer is option 1.

Concept:

Plain text is the information that is converted during encryption. Plain text is a broad word in computing for data that solely represents characters of readable information and not its graphical representation or other elements.

• Plaintext in cryptography is often regular readable text before it is encrypted into ciphertext, or readable text after it has been decoded.
• The ciphertext is the encrypted text that has been converted from plaintext by an encryption technique.
• Ciphertext cannot be read until it has been decrypted (converted to plaintext). The decryption cipher is an algorithm that converts ciphertext to plaintext.

Hence the correct answer is Plain text.

The correct answer is Rice.

• Rice blast disease, caused by Magnaporthe oryzae (Ascomycota), occurs in about 80 countries on all continents where rice is grown, in both paddy fields and upland cultivation.
• The extent of damage caused depends on environmental factors, but worldwide it is one of the most devastating cereal diseases, resulting in losses of 10–30% of the global yield of rice.
• Other common diseases of the crop of rice are - Blight, Bacterial leaf streak, Brown spot, Sheath blight, False smut, etc.

Additional Information

• The biological agents that causing diseases to plants are known as pathogens. 
• Some of the viral diseases in plants are - bud blight (soyabeans), Curly tops (Beans, tomato, etc.), Mosaic leaf (Tomato, pea, potato,tobacco, etc.).
• Some of the bacterial diseases in plants are - Blights (vegetable crops), Bacterial wilts (Tobacco, potatoes, etc), Cankers (Woody plants), Leaf Spots, Soft Wrots, etc.
• Some of the fungal diseases in the plants are - Cankers, Ergot, Rusts, Root rots, Scabs, Smuts, etc.