Read this excerpt from “The World” by Christian Rossetti:

Acquiring english is a way of learning where you learn english by birth, this includes listening to your parents, brothers and sisters and on the whole learning it from the environment around you while mastering standard english need qualified institutes and teachers who make certain programs and syllabus to you master the standard english. this also can include a long session of academic studies before you can master the standard english.standard english is necessary for literary works, official usage and writing materials for standardized publications or when someone needs to speak publicly. in most cases the employers of a company also demand and like the use of standard english from their employees. 

The answer is c, because it's referring to you, and then refers to a group of people stopping the flu, which is a clever way of making the viewer feel like they have the impact to stop a disease. (sorry its hard to explain)