It is usually not quite cold in this area in March, but sometimes temperature __________be very low.
| A．should | B．can | C．must | D．shall |
The silence in the dark building was scaring. No sound and voice____ heard at that moment.
| A．Were | B．Was | C．Is | D．are |
If _____ without following the doctor’s instructions, the medicine may have serious side effects.
| A．Taken | B．to be taken | C．Taking | D．being taken |
________ you happen to see Mary, would you please ask her to come here?
| A．Would | B．Could | C．Should | D．Might |
Everyone knows that _______ is dangerous to play with fire, but _______ is difficult is to prevent children from playing with fire.
| A．it, it | B．what, what | C．it, what | D．what, it |
Not until the early years of the 19th century ________ what heat was.
| A．man did know | B．did man knew |
| C．didn't man know | D．did man know |