Which of the following is a question of value?

a. "What are the causes of autism "

b. "Is human cloning ethical "

c. "How does a car engine work "

d. "Should the drinking age be changed "

We can definitely reject options a) and c) - those are questions with absolute answers, which ask about a mechanism of something.

Both b) and d) include values, but option b is the correct one - it more directly asks about a value, while option d can be influenced by a value but does not directly ask about it.