Question

Assertion (A) Algae are the primary producers of many food cycles.
Reason (R) Half of the total carbon dioxide-fixation on earth is carried out by algae.

• A. If both A and R are true and R is the correct explanation of A
• B. If both A and R are true, but R is not the correct explanation of A
• C. If A is true, but R is false
• D. If A is false, but R is true

Answer 1

Answer: (B)

Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
Algae are of paramount important as primary producers of energy rich compounds which form the basis of the food cycles of all aquatic animals. Many species of Porphyra, Laminaria and Sargassum are among the $70$ species of marine algae used as food.
Algae also perform $CO _{2}$-fixation on earth through photosynthesis. They increase the level of dissolved oxygen in their immediate environment.