Question

In which sentence does an adverb clause modify an adverb?
1.0The scientists studied the sun as the eclipse’s shadow swept across Earth.
2.) A full lunar eclipse lasts longer than a partial eclipse.
3.)We used safety goggles when we viewed the eclipse.
4.) When people did not understand the science behind an eclipse, they were afraid of the solar and lunar events .

Answer 1

The correct answer to the question stated above is:

The scientists studied the sun as the eclipse’s shadow swept across Earth. 

Adverb clause consists of words which function as an adverb. It can modify verbs, adverbs, and adjectives by providing conditions to describe them. 

Answer 2

The snetence in which an adverb clause modifies an adverb is "The scientists studied the sun as the eclipse’s shadow swept across Earth." Option A is correct.

Adverb clause consists of words which function as an adverb. It can modify  or describe verbs, adverbs, and adjectives by providing conditions.

Adverb clauses can be employed to add explanatory detail to your writing and explain how or why things happen.