あの子には手を焼(や)いています。
a. I burned that boy’s hands.
b. I’m warming up that boy’s hands.
c. I find that boy difficult to deal with.
d. I love that boy so much.
手(て) is a hand and 焼(や)く is a verb for “burning,” “grilling” and “pan-frying” but 手を焼(や)く is a set expression to mean: to be at a loss what to do 《with》, to be unable to control, to find a person a tough customer
So the answer is c.
あの もんだいには 手を 焼いた。
I struggled with that problem.
この 生徒(せいと)には 手を焼くだろう。
This student will give me a hard time.