六. 语法应用
1. When Mark opened the door, he saw a women standing there. He ______ her before.
A. never saw B. had never seen C. never sees D. has never seen
2.He ______ more than 5000 words when he entered the university at the age of 15.
A. has learned B. would have learned C. learned D. had learned
3. Father____ for London on business upon my arrival, so I didn’t see him.
A. has left B. left C. was leaving D. had left
