To understand the grammar of the sentence，you must break it______ into parts．
| A．down | B．up | C．off | D．out |
--- This returned Chinese scholar has become one of the top experts in this field.
--- Yes, I know him very well. He_________in Africa on wild animals for eight years.
| A．has worked | B．had worked |
| C．worked | D．has been working |
.They turned out more than 1,000 washing machines, most of which ________quality.
| A．is good | B．are good | C．is of high | D．are of high |
-- Did you visit the zoo?
--- No, we_______have visited it, but we spent too much time shopping.
| A．shouldn’t | B．can’t | C．could | D．must |
.The letter from his girlfriend he had been looking forward to _________yesterday.
| A．came | B．comes | C．coming | D．come |
.Jack, it’s________bad manners to blow your nose at________table.
| A．the; a | B．the; / | C．/; the | D．/; / |