#### Answer

4 ways

#### Work Step by Step

A test has four true/false questions.
When only one answer is true, the number of combinations is equal to the number of questions:
true
false
false
false
false
true
false
false
false
false
true
false
false
false
false
true
It's obvious there cannot be more than four combinations, because there are no other questions to have the answer as true, and we need to have only one answer be true.
There are $4$ ways for one answer to be true and three false.