Answer:
A. Metaphor
B. The phrase, "My grandfather's garage was a treasure chest" is comparing a old garage to a chest of priceless and valuable treasures, likely because they meant a lot to his grandfather, who didn't want to let go of these items.
Step-by-step explanation:
My grandfather's garage was a treasure chest of gadgets, garden tools, car parts, sports equipment, and even musical instruments he had acquired and couldn't let go
Similes use "like" or "as" to compare unrelated things. Therefore simile is not the answer.
Extended Metaphors are metaphors that go on for a long time such as multiple sentences or the duration of an entire book. Therefore extended metaphor is not the answer.