1. to be sorry
2. to feel apologetic
3. sorry!

1. underground railway; subway
2. subway train

1. thread
2. string
3. wire
4. line
5. (after a number) tier (unofficial ranking of a Chinese city)

classifiers: 條, 股, 根

1. to go
2. to go to (a place)
3. (of a time etc) last
4. just passed
5. to send
6. to remove
7. to get rid of
8. to reduce
9. to be apart from in space or time
10. to die (euphemism)
11. to play (a part)
12. (when used either before or after a verb) to go in order to do sth
13. (after a verb of motion indicates movement away from the speaker)
14. (used after certain verbs to indicate detachment or separation)

1. city center
2. downtown