What distinguishes user acceptance tests (UATs) from validation tests?

A.
UATs require a trial run to construct a baseline, while validation tests never require initial
baselines.

B.
UATs analyze at all OSI layer from 1 through 7, while validation tests stop at Layer 3.

C.
UATs test applications, while validation tests only test connectivity.

D.
UATs tests applications as they are used by real users, while validation tests check specific
functionality.