Judge the following sentence according to the criteria given below: Reef-building corals are not able to survive in nutrient-poor tropical waters BECAUSE they receive most of their nutrition by capturing tiny planktonic food with their stinging tentacles.

A, The assertion and the reason are both correct, and the reason is valid.
B, The assertion and the reason are both correct, but the reason is invalid.
C, The assertion is correct, but the reason is incorrect.
D, The assertion is incorrect, but the reason is correct.
E, Both the assertion and the reason are incorrect.

Coral reefs are found in the tropical water which is poor in nutrients. The species of coral that form the reefs have symbiotic zooxanthellae in their tissues that can carry out the process of photosynthesis. The coral reefs obtain their food from their symbiont and hence, can survive in the water that lacks enough supply of nutrients.

Coral reefs also use their stinging tentacles and capture the small animals to feed on them. However, the food derived from symbiont zooxanthellae is the major source of nutrients for them.