选择与句中画线部分意思相同或相近的词或短语。
1. Mary called him three times yesterday, but nobody answered.[ ]
A. visited
B. gave a message to
C. told
D. phoned
2. Jim comes to Visit us sometimes.
That is always the happiest time for the whole family. [ ]
A. on time
B. all the time
C. at times
D. many times
3. Jimmy tried hard, and in the end he did it well. [ ]
A. at first
B. at the beginning
C. at the end
D. at last
4. —Oh, sorry, John. I forgot to post your letter.
—That's all right. I'II post it myself.
[ ]A. Never think about it
B. It doesn't matter
C. Don't be sorry
D. I don't care
5. —Hello! May I speak to the headmaster?
A. Speak louder
B. Wait a moment
C. Call again
D. Speak out
试确定参数a的值，并求矩阵A．