76. Sad as it is, the unemployment is unlikely to go down this year.
77. Without absolute secrecy, the mission wouldn't have succeeded.
78. It can't have been Mr. Phong you saw yesterday because he has been in Hanoi for a week.
79. You've got the wrong end of the stick.
80. They arrived at the station in the nick of time.
Chúc bạn học tốt !!!