Answer:
I would say C, noise.
Step-by-step explanation:
This is because noise, such as loud speaking, are distractions towards work, studying, and other things that involved the process of thinking. when you are doing a test for example and the entire class is talking, it's a bit harder to exceed at your test because of all the commotion around you. Let's say your in a library, as you may know, everyone is quiet and if people are talking librarians would say "shhhhh". its for the reason of people studying, reading, doing work, etc, that you have to stay quite son they can focus as much as possible.