Question

plastics and coral reefs
after diving in the verde island passage in the philippines looking for a specific species of fish, marine biologist hudson pinheiro saw something else—lots of plastic. after that dive, pinheiro began studying fish and plastics, and his findings were troubling. pinheiros study appeared recently in nature and is touted as one of the most comprehensive catalogs of the plastic covering the coral reefs. the type of plastics pinheiro found included plastic bags and bottles, but an enormous number of ropes, lines, and nets showing researchers that even when the sport of fishing concluded, it continued deep in the ocean from the leftover debris.
which choice best describes the function of the underlined sentence in the overall structure of the text?
it summarizes how plastics can harm coral reefs, fish, and other marine mammals.
it presents the fish hudson pinheiro reviewed and why he dove that day in the philippines
it explains why hudson pinheiro conducted research to learn more about plastics in the oceans
it states the hypothesis of the researcher hudson pinheiro developed to study plastics

Explanation:

The text starts by talking about Pinheiro diving for a fish species but seeing lots of plastic. The underlined sentence "After that dive, Pinheiro began studying fish and plastics, and his findings were troubling" shows the cause - effect. The cause is seeing plastic during the dive (which was for fish), and the effect is starting the research. It's explaining the motivation behind his research on plastics in the ocean.

Answer:

It explains why Hudson Pinheiro conducted research to learn more about plastics in the oceans.