Question

the atlantic cod was once the mainstay of the united states fishing industry. however, warming of the ocean along the shores of new england has caused the stock of cod to disappear almost completely. according to scientists at the gulf of maine research institute, the gulf of maine is heating up faster than a majority of the rest of the planets oceans. as a result of warmer ocean waters, female cod produce fewer offspring, and these fish are less likely to survive to maturity. even though recreational cod fishing was banned in 2014, and strict limitations were placed on the number of fish commercial fishermen could catch, these measures have not been enough to protect the cod. what is the main, or central, idea of the passage? because the gulf of maine is warming unusually quickly, atlantic cod are disappearing. because cod used to be abundant in the atlantic, it was once the backbone of the u.s. fishing industry. female cod are producing fewer offspring in the gulf of maine.

Explanation:

The passage starts by noting cod was a mainstay of US fishing, then focuses on ocean warming (Gulf of Maine heating fast) causing cod stock to disappear, with details on reduced offspring and survival, and that fishing restrictions didn't help. The first option captures the main cause (unusual warming) and effect (cod disappearing). The second option is a background detail, and the third is a supporting detail of the main cause - effect.

Answer:

A. Because the Gulf of Maine is warming unusually quickly, Atlantic cod are disappearing.