By the end of this year, Tom ________ English for three years

77. By the end of this year, Tom ________ English for three years.
A. has studied            B. will be studying            C. will have studied      D. has been studying
78. In 2014 a robot named Philae, part of the Rosetta mission, ______ landed on a comet.
A. success              B. successfully          C. successful               D. unsuccessful
79. Mai is really good at English. She practices _______ English every day.
A. speak                     B. to speak                             C. speaking                           D. spoke
80. Jane: ‘Why don’t we have a look round the campus?’
    Mary: ‘_________________’
A. Yes, why not?                  B. Yes, thanks                       C. It’s my pleasure    D. Do we?   
81. My house was very dirty because I ______ it for weeks.
A. hadn’t cleaned            B. didn’t clean             C. haven’t cleaned            D. don’t clean
82. Lan spoke English ______ after she lived in England for several months.
A. nature                    B. natural                                           C. naturally                           D. unnaturally 
83. She spent the whole day ______ in her office, so she came home exhausted.
A. work                                  B. working                 C. to working                        D. worked