Information processing rate can be a barrier to listening because
a. people are hardly ever capable of processing information as fast as most speakers speak
b. people are normally capable of processing information faster than most people speak
c. there is such a wide variety of processing abilities among people that no matter how fast or slow you speak, it will not be appropriate
d. recent research shows that there is little connection between speaker rate and effective listening

I believe that most relevant answer in this item is:

b. people are normally capable of processing information faster than most people speak

Among the four choices above, we choose b rather a, c, and d. This is because this choice is rather correct than the other three.

Let us complete the sentence:

Information processing rate can be a barrier to listening because people are normally capable of processing information faster than most people speak

Thus,

the correct answer is B

answer; i believe that the correct answer is (d); // supercontinent