Question

_____ muscles bend bones, and ________ muscles straighten bones.
a.
extensor, flexor
c.
flexor, extensor
b.
flexor, flexor
d.
extensor, extensor

Answer 1

Hint: Do you really think the same muscle would bend and straighten bones? Think about antagonist muscle pairs.

Just think about the words a little. What do you think a flexor muscle does? Flex
Extensor muscle? Extends

That should be enough to help you figure out the correct answer. If that doesn't help, then there is Google. :)