$(2)$ A and $B$ are two almost identical images. If $|A-B|$ is performed, which of the following statements is true?

a$.$ The histogram of the difference image has a high peak around $(0).$

b$.$ The difference image is a measure of the gradient.

c$.$ The difference image can be used to spot changes in object colors.

d$.$ a and $b$

e$.b$ and $c$

f$.$ a$,$ b and c