Question

a mangrove forests tangled roots provide good hiding places for aquatic organisms. choose 1 answer: a no change b forests tangled roots c forests tangled roots d forests tangled roots

Explanation:

The sentence is talking about the tangled roots of a single mangrove forest. The possessive form for a singular noun is formed by adding's. "Mangrove forest" is singular here, so it should be "forest's tangled roots".

Answer:

B. forest's tangled roots