Who surrounds themselves with a personal bubble (personal space)?

Personal space is practically universal concept familiar to all humans. Its basis is biological but depends heavily on cultural factors. In chilly Scandinavia, people prefer a good deal of personal space. It is not uncommon to see people at a bus stop two meters apart. In contrast, other places like Italy see physical closeness and contact as an important part of developing and maintaining social bonds.

Carbon monoxide is usually more dangerous indoors.

Idont know which one is right   but i know that c is wrong and a might be wrong