_________the difficult problem,the professor continued to do his experiment. [ ]

____on rocks, the plant grows to abush,_____broad leaves and large flowers.

I often chat with my friends on the Internet.— You are so smart! Will you please tell me____?

foreign(外国) friends come to visit China every year.

What’s your uncle’s opinion about your decision?—He always encourages me to do ________ I think I should.