AT89C51单片机有4个P口，分别是：
A. P0、P1、P2、P3
B. P1、P2、P3、P4
C. PA、PB、PC、PD
D. A、B、C、D
The author stopped at a village on his way because he wanted to ____.
A. have his car repaired
B. enjoy the beautiful scenery
C. look for some bananas to fix his radiator
D. talk to some villagers to learn about their way of life
What's the author's reaction to the man's remarks on the center of the earth?
A. He thought the man was serious about what he said.
B. He thought that the man was telling the truth.
C. He thought that the man was telling a story.
D. He thought the man was making fun of him.
What does the author come to learn from the man's remarks?
A. The rock mentioned by the man is really the center of the world for everyone.
B. There are lots of such "rocks" in the world representing the center of the world.
C. There is only one center in the world that is actually in New England.
D. As a matter of fact, the center of the world does not exist in his opinion.
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