Mike is designing a new brand of earphones. He needs to make the ear phones small enough to fit inside a person's ears. But if the earphones are too small, the speakers inside of them will not be able to generate a high-quality sound. Mike also knows that the earphones will be used by people as they exercise. So he needs them to be able to withstand sweat as well as hot and cold weather.

only b 

Allow large amino acids through

Volcanoes make new rocks so not ahotspots are the the stuff that makes volcanoes mid atlantic ridge(mar cause i’m lazy) is a constructive plate boundary so it makes sense that new rocks would be found near it, also the mar is in the middle of the ocean so it fits the description deep ocean trench, umm, there’s no ocean trenches to where you’re goingso the mar is most likely the answeri wouldn’t trust me but hey why not