—It’s a long time since we met last. Haven’t you graduated from college yet?—_____. I ______ English for four years in Nanjing University.
If he ___ me his telephone number yesterday, I ___ able to ring him up now.
The internet has made ____ possible for everyone to talk with friends miles away.
The _________ at the military academy is so rigid that students can hardly bear it.
I remembered _____ the door before I left the office, but forgot to turn off the lights.
Teachers required that all the students ___ their homework all alone.