It’s hard to say what kind of person he is. Sometimes he is very nice; at other times he _______ be very cold.

Such a good opportunity may not come again, so you ____________ let it go this time.

—How dangerous it was!—Yes，but for the passer­by’s quick action，the girl ________.

 Although this         sound like a simple task, great care is needed.

——Ms Lin looks rather a kind lady.——But in fact she is cold and hard on us. You ____ believe it!