57. The passage mainly talks about _____.

A. dementia―a threat to the old people                B. modafinil―a nice drug for dementia

C. relevant drugs to a better brain                        D. cognitive enhancement

56. According to the message, we can learn that originally modafinil is a drug designed for _____.

A. for both healthy and unhealthy people

B. the treatment of dementia

C. people who can hardly go to sleep

D. those suffering from falling asleep suddenly

54．A．confirmed           B．acknowledged      C．negotiated           D．managed

53．A．peace                  B．friendship            C．trust                    D．harmony

52．A．rising                  B．starting               C．falling                 D．turning

51．A．reasoning            B．quarrelling          C．debating              D．discussing

50．A．however              B．though                C．but                     D．and

49．A．allowed               B．convinced            C．forbade               D．promised

48．A．pushed                B．felt                     C．talked                 D．fought