用括号内所给动词的适当形式填空。
I ________ (read) a novel last night when I heard knocks at the door.
The young man ________ (live) alone since he graduated from college.
Be careful ___________ (not fall) off the ladder.
The actor and director ________(be) coming to give us a speech next weekend.
I overslept this morning. By the time I got to the train station, the train ________ (leave).