Which gas do plants absorb from the atmosphere for photosynthesis?

(A) Oxygen
(B) Nitrogen
(C) Carbon monoxide
(D) Carbon dioxide

The answer is: (D) Carbon dioxide
Plants primarily absorb carbon dioxide (CO2​) from the atmosphere for photosynthesis. The photosynthesis is the process that plants use to convert light energy into chemical energy, which is stored in glucose (sugar). This process is essential for most life on Earth as it produces the oxygen we breathe.

Which vitamin is produced in human skin in the presence of sunlight?

(A) Vitamin A
(B) Vitamin B
(C) Vitamin C
(D) Vitamin D

The answer is: (D) Vitamin D
The vitamin produced in human skin in the presence of sunlight is vitamin D.
When exposed to sunlight, a cholesterol-based compound in the skin called 7-dehydrocholesterol is converted into previtamin D3. This previtamin D3 then spontaneously transforms into vitamin D3, which is the form that is transported to the liver and kidneys to be converted into its active hormonal form.