Answer:
The sentence that is a call to action is:
B. Please contact your local representative to voice your support.
Step-by-step explanation:
A call to action is usually an imperative sentence whose purpose is to get people to perform a certain action. It may sound as a command or as an invitation, depending on the context, but in any case it tells us to do something. Imagine an ad about a brand of juice that, in the ends, says, "Drink this brand of juice!" That is an example of a call to action.
With that in mind, we can choose letter B as the best choice. It is an imperative sentence asking people to perform a certain action: to call their local representatives.