Which region of your brain controls your right side? 

The muscles on the right side are affected by the left frontal lobe. Similarly, the muscles on the left side of the body are controlled by the right frontal lobe. 

Each lobe is in charge of operations on the opposite sides of the body: the left hemisphere is in charge of the right side, and vice versa. 

The left frontal lobe is thought to be the most prominent lobe, and it is responsible for language, rational reasoning, and reasoning skills.

Therefore, the correct answer is the left frontal lobe.