A is one reasonable answer.
It's to show an exception (which is often the purpose of "yet") because in the first clause it identifies an action, then then it's like "but wait, maybe the action didn't really get going" in the second half of the sentence
If the options are metaphor, alliteration, allusion, and apostrophe, I believe the answer is metaphor, because the others don't fit.
Alliteration is the repetition of a consonant.
Allusion is reference to something or somebody outside of that literary work.
And apostrophe is the author speaking directly to somebody outside the poem, usually gods or a muse.
Answer:
urgence, haste, swiftness, quickness
Explanation:
B
I think it should change into “The test subject will be observed for the next few days.”