I guess formal and informal refer to two types of essay - you can write a formal essay where you avoid conversational language and such and where you need to be very professional, or you can write informally where you don't have to think about such things, it is very casual.
Answer:
A. before you leave
Explanation:
It a phrase that can’t stand on it own because it wouldn’t have meaning.
They’ve theme is that the power belongs to the people and that it is the responsibility of the equal people to correct the government
