Select the most appropriate option to fill in the blank.
The scientists revised their hypothesis _____ new data had emerged contradicting their initial assumptions.

Correct option is C

The correct option to fill in the blank is (c) because.

Explanation:
The sentence indicates a cause-and-effect relationship. The emergence of new data was the reason why the hypothesis was revised. 'Because' is used to introduce the reason.

Example: The flight was delayed because of the heavy fog.

Information Booster:
Subordinating conjunctions like 'because', 'since', and 'as' are used to link a result with its cause.

So the correct answer is (c)