----This returned Chinese scholar has become one of the top experts in this field.
----Yes,I know him very well.He_________in Africa with animals for eight years.
| A．has worked | B．had worked | C．worked | D．has been working |
The _______ price will save you one dollar for each dozen.
| A．reduce | B．reducing | C．reduced | D．reduces |
The student corrected his paper carefully, _______ the professor's suggestions.
| A．follow | B．following | C．followed | D．being followed |
He went from door to door, _______ waste papers and magazines.
| A．gathering | B．gathered | C．gather | D．being gathered |
. _______ the office, the foreign visitors were shown round the teaching building.
| A．Having shown | B．Showing | C．Has shown | D．Having been shown |
With winter _______ on, it's time to buy warm clothes.
| A．came | B．comes | C．come | D．coming |