The cattle _______ grazing on the grass.
A. were B. was C. be D. is
Such a problem is＿＿＿＿difficult for a primary school student ＿＿＿.
A. so； to work B. very too； to work out
C. rather too； to work out D. quite too； to answer
— What does the sign over there read?
—“No person __________ smoke or carry a lighted cigarette，cigar or pipe in this area.”
A. will B. may
C. shall D. must
The best times to visit Shangri-la are spring and autumn ____ the temperature is at its mildest.
A. when B. where C. that D. which
Scientists study ____ human brains work to make computers.
A. when B. how C. that D. whether
______ in the school campus in spring, we will always noitce a colorful display of flowers.
A. Walk B. Having walked C. Being walking D. Walking
