Aptitude tests are designed to measure one's:

A) potential for learning a skill or body of knowledge.
B) achievement in a particular subject.
C) capacity for divergent thinking.
D) verbal abilities only.

Aptitude tests are specifically designed to measure one's potential for learning a skill or body of knowledge, rather than focusing solely on current achievement or specific subject knowledge. This can include measures of cognitive abilities such as reasoning, problem-solving, spatial visualization, and other factors that are important for success in many different fields. While verbal abilities may be included in some aptitude tests, they are not the only focus.