I cannot______ puzzled，for I simply cannot understand how I could have made such a stupid mistake.

In a few years’ time, there ______a lot of trees around the house.

Can I help you?—Yes, I bought this radio here yesterday, but it _____________.

It’s the third time ____ I have been here.

Look! Who is the man in the picture（图片）?——I know. ______ Zhou Xingchi.