What does the opacity effect do?
a. changes the transparency of the fill and stroke at the same time
b. changes the transparency of the fill and stroke separately
c. makes the fill and stroke look hazy or blurry
d. chooses a random color from the wheel tab

The correct choice is C! Hope this helped.

Explanation:

A. Changes the transparency of the fill and stroke at the same time is the correct answer.

Explanation:

According to Adobe User's Guide "a layer’s overall opacity determines to what degree it obscures or reveals the layer beneath it," meaning that the closer the Opacity is to zero, the more transparent a layer is. So, it means that the fill and stroke are affected at the same time, making A the correct answer.