All of the following are reasons that visual aids are useful in speech delivery except:
a. they demonstrate something.
b. their presence allows the speaker to take a rest from talking.
c. they expand understanding.
d. they add interest to a speech.

The following are reasons that visual aids are useful in speech delivery:
>Visual aids add interest to a speech.
>Visual aids demonstrate something that is related to the speech.
>Visual aids expand understanding.
Therefore, the answer is option B. The presence of visual aids does not allow the speaker to take a rest from talking.

If it is said that deliberate thinking consists of search and inference so one should search for common framework that might assert this way of thinking,  a certain object and then one should make inferences from and about the object found.