Which of the following describes an estuary?
A. has different levels based on how much sunlight
reaches that depth and is the largest marine biome
B. located in the photic zone and warm tropical waters
with build up of many layers of dead cnidarians
C. found where land and water meet and is covered by
water at high-tide then dry at low-tide
D. where freshwater streams meet the ocean and is a
breeding and feeding spot for birds and fish

D. where freshwater streams meet the ocean and is a  breeding and feeding spot for birds and fish

Explanation:

Estuary is an area of freshwater where freshwater streams meet the ocean and also a  breeding as well as feeding place for birds and fishes. This estuary is the place of habitat for large number of biotic factors includes plants and animals such as shrimp, fish, and oysters etc. The population of these animals are lower due to human activities that cause pollution in the estuary which leads to death of animals.

answer: the answer is b

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.