A brillia
nt idea occurred to him, ______ to his research in the lab.
| A．while devoting | B．while devoting himself |
| C．while he was devoted | D．while devoted |
______I understand your viewpoint, I don’t agree with it.
| A．Unless | B．Since | C．Before | D．While |
Do you know when the Great Wall _________?
| A．was come into being | B．came into being |
| C．had come into being | D．had been come into being |
He tried his best to solve the problem, _______difficult it was.
| A．no matter | B．no matter how | C．whatever | D．although |
This film_________ the scenes of my childhood.
| A．called up | B．called on | C．called out | D．called for |
—Do you think playing cards is beneficial to our study?
—No，if ________，it can help us kill time when we have nothing to do.
| A．something | B．anything | C．nothing | D．everything |