Each one of the following sentences contains a clause. in which sentence is the clause used as an adverb?
a. what you really need is a back massage.
b. all of the delegates who have actual opinions should keep silent.
c. whales, which eat krill, prefer colder ocean waters.
d. i do not mind fishing, as long as i don't have to bait the hook.

Oceans produce approximately 80 percent of the oxygen our planet needs to support animal life. pollution that reaches the ocean through dumping, oil leaks, runoff, and other processes interferes with that oxygen production and poses a real threat to the oxygen content in our atmosphere. if the oxygen content decreases, it is likely that carbon dioxide will increase. this could have dramatic consequences for life as we know it. which does this passage indicate causes a decrease of oxygen in the atmosphere?