polluted water kills the coral reefs. the coral reefs are fragile. we should keep the ocean clean. combine…

Brief Explanations:

Combine the key - ideas of the three sentences. The first two sentences explain the problem (polluted water harming fragile coral reefs) and the third is a call - to - action.

Answer:

Since the coral reefs are fragile and polluted water kills them, we should keep the ocean clean.