This is a word relationship question. Before touching the options, name the relationship in the given pair in plain words: "recommence" (begin again) and "suspend" (pause or stop) describe opposite actions, one restart, one halt. So the blank must also be filled by the opposite of "nonchalant."
"Nonchalant" means unconcerned, calm, and not showing worry. Its opposite is a word describing someone weighed down by trouble or anxiety.
Only "beleaguered" gives a true antonym of "nonchalant," matching the antonym relationship of "recommence" and "suspend."
Let's summarize:
So the answer is Option B, beleaguered.