2. what is a boycott? why is it effective?

A boycott is a sort of protest of something by refusing to use/buy/associate with it. It's effective because if you, for example, boycott a store or product, you are not buying what they are selling. They need people to buy their stuff, so if enough people join a boycott, they (the store or product) will be forced to listen to the buyers' demands or go out of business. Hope this is helpful!

he sent troops to protect the students as they entered the school.

well that depends on how deep the hole is. you'd first go through te crust of the earth, then the upper mantle, then the lower mantle then the outer core, then the inner cor then you'd be stuck in the core to melt.