________ on ten years of observation and study, Professor Wang announced that everyone dreams every night，whether they realize it or not.
| A．Basing | B．Based |
| C．Been based | D．Having based |
—Ouch! You hurt me.
—I'm sorry. But I ________ any harm. I ________ to drive a rat out.
| A．don't mean; am trying |
| B．didn't mean; tried |
| C．haven't meant; tried |
| D．didn't mean; was trying |
In general, most tennis ________ on hard courts or on clay.
| A．plays | B．is played |
| C．has played | D．has been played |
Despite ongoing street protests, US beef ________ in South Korea due to its lower price.
| A．is sold well | B．sells well |
| C．sells poorly | D．is sold poorly |
Today many physical bookstores ________ down with financial difficulties, inflexible management strategies and competitive pressure from online bookstores.
| A．had closed | B．having closed |
| C．being closed | D．are closing |
—Look, I've got admission to Harvard University for a shortterm study next semester.
—How fantastic! You ________ a different university life then.
| A．have experienced | B．will be experiencing |
| C．have been experiencing | D．will have experienced |