_________ the math problem is difficult, I’ll try hard to work it out.A. When B. Though C. Before
_____ he is only 4 years old,he is able to play the piano very well.
Working hard ________ the key _________ success of everything.
We feel like ___________ the work as soon as possible.
The old man lives _______ in the countryside, but he didn’t feel __________.
He didn’t know English at all, so he can’t understand __________ the machine.