Green products are becoming more and more popular because they are environmentally ______. [ ]

There is a lot of smoke coming out of the teaching-building there.—Really?It _________ be a fire,most probably.

.—When did you ______English?—When I was in college.

Li Na is famous all the tennis fans in China know her.

etty go shopping with you yesterday—Even if she _____ a lot of studying, shewould have preferred staying home to going shopping．