Answer:
A. change activity.
Step-by-step explanation:
Restiveness is the anxious feeling that a person has, an ill foreboding feeling of something to happen. It is the feeling or act of being impatient.
In a listening situation, if a speaker sees that his listeners are becoming restive, then he should try to change the activity he's doing. This will ensure that the listeners are not bored and impatient and it will divert the attention of the listeners. It will also provide relief or change in the interest of the listeners.
Thus, the correct answer is option A.