Question

what is never to be engaged when using power tools?
booster
bit shank
trigger lock

Explanation:

A booster is not something that should never be engaged when using power - tools. A bit shank is a part of the tool that holds the bit and is necessary for operation. However, the trigger lock is designed to prevent accidental start - up and should not be engaged during normal use of the power tool as it defeats the purpose of the safety feature.

Answer:

C. trigger lock