In which sentence does an adverb clause modify an adverb?

1.)the 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: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

bradykinin is a physiologically and pharmacologically active peptide of the kinin group of proteins, consisting of nine amino acids.