40.
Your Answer is
Correct Answer is J
Explanation
According to the sentence meaning "These bats transmit high-frequency sounds and use echoes to locate their prey", so it is judged that send out and use are the two predicates of the sentence, so item J is correct.
F/G/H item: Doing and to do are non-predicate verbs and cannot be used as predicate verbs, so F/G/H is wrong.