In Which of the Following Conditions Is the Site Exclusion

In which of the following conditions is the Site Exclusion tool used?

A) When campaign shows irrelevant clicks.
B) When the campaign shows a very high number of clicks, but a very low conversion rate for a specific placement.
C) When the campaign shows a very low number of clicks, but a very high conversion rate for a specific placement.
D) When campaign shows relevant clicks.