I would say it would be rigid because the definition of supple is easily bent.
D. Mom should be capitalized because I believe it is a proper noun.
You can replace the word mom with a person's name. That is not always the case however. For example, I called my mom on my.... If you capitalized mom in this sentence and put a name then it wouldn't make sense because the word my was added. Hopefully this helps and makes sense. Good luck!!!
"deer in headlights" is an idiom.
"like deer in headlights" is a simile, the word "like" makes it a simile.
Answer:
"the strongbox is still safely hidden beneath a hollow stair. They’re alive, and the house is still standing. "
"when Mattie hangs Grandfather’s sword, there’s a sense that his role as protector of the house is being transferred to her."
