You are reading about a new psychological test that claims to measure "motivation." If the test is supported by lots of research showing that it is "valid," what would this mean?

a. It means that it is not possible for the people taking the test to fake their level of motivation.
b. It means that when people take the test on two occasions, they get similar scores both times.
c. It means that there is a predictable and consistent way that the test is administered and scored.
d. It means the test is actually measuring motivation, instead of perhaps measuring something else.