6.On our way to Beijing, we visited Xi’an, a city of two million _______, and stayed there for two days.
A. insects B.human C.inhabitants D.flights
7.One of the main reasons for air pollution is that many cars _______ smoke into the atmosphere.
A.gather B.hire C.discharge D.escape
8.Don’t forget to _______ to let us know you arrived safely.
A.cable B.cage C.border D.bay
9.She gave him a _______ that she could not come to his party.
A.mistress B.shoot C.neck D.hint
10.When the temperature is below zero, water will _______.
A.freeze B.virtue C.sink D.seek
6.C 7.C 8.A 9.D 10.A