Which of the following is true about reliability?

A) Reliability is basically a "yes" or "no" question. A test either is or is not reliable.
B) A test does not need reliability if it has good face validity.
C) If a test has reliability, it also has validity.
D) A test's reliability is shown by how well the test items correlate with each other.

Reliability refers to the consistency and stability of a test's results over time and across different test administrations. One way to measure reliability is by assessing the correlation between the different test items. If the items are highly correlated, it suggests that the test is consistent in measuring the same construct. Therefore, D is the correct choice as it accurately describes how a test's reliability is shown. A, B, and C are incorrect as they do not accurately describe reliability.