Gaps in rock layers are called a. unconformities c. half-lives b. index fossils d. none of the above select the best answer from the choices provided a b c d

It's unconformities. So A is correct.

a. unconformities

Explanation:

Uncinformity is a geological disturbance. It can be found as a gap between the rocks due to the deposition of sediments inside the rocks. The rocks which exhibit unconformity are generally younger than the one buried below.