The correct option is C tiring
“Tedious” means too long, slow, or dull; tiresome or monotonous.
Option C is the correct answer because “tiring” means causing one to need rest or sleep as it is fatiguing, hence it is the correct answer because what is tedious will need you to have patience and want rest, hence it is correct.
Option A is incorrect because “easy” means something that is done without great effort, which is incorrect here.
Option B is incorrect because “difficult “ means something that is hard to do, while tedious means something that is boring or monotonous, they are two different meanings
Option D is incorrect because “troublesome” means something that causes a lot of trouble which is not the correct meaning of the given word.