Tu Youyou was ________ the 2011 Lasker clinical Medical Research Award on September 12 because she discovered a drug called artemisinin ________ against malaria.
| A．presented；using | B．presented；used |
| C．present；to use | D．presenting；used |
51. After everyone took_______ place, the meeting began.
| A．his | B．their | C．there | D．the |
52. －Why don’t we take a little break?
－Didn’t we just have _______?
| A．it | B．that | C．one | D．this |
53. If you want to change for a double room you’ll have to pay ___$15.
| A．another | B．other | C．more | D．each |
54. We should always keep ______ well-informed of the changing information.
| A．us | B．ours | C．ourselves | D．we |
55. Give the message to ______ is at the table.
| A．whomever | B．whosever | C．whatever | D．whoever |