Interference, in simple terms, is the act of anything that disrupts the smooth flow of things. It can also be defined as something or anything that blocks or obstructs things from moving forward, disturbing the functioning of that act.
In a speech communication process, the various issues like an upcoming job interview, lack of air conditioning, or even a toothache are all examples of interference. They are all elements of any obstruction that might hamper the smooth act of delivering the speech.
I think it is C, because if I'm right present principal is something that is happening presently? If so, C would be the answer because they "are doing" the exercises right now in context.
