根据短文理解, 从A、B、C、D四个选项中选择最佳答案填空。

    Mr. Brown lived in a small town. One day he  1 a long journey. It was very late when he was going home.  2 he found that a man 3behind him. Mr. Brown went faster, and the man walked faster too.  4Mr. Brown walked slowly and the man walked slowly 5  .

    Now they were coming near a garden. Quickly, Mr. Brown ran6  it. He tried to get away from the man in this way, but he failed. He was very afraid. He rushed and the man rushed after him. Then Mr. Brown stopped. "Excuse me, "he said, "what do you want 7?"

    " 8 , sir, "answered the man, "You see, I have to  9 Mrs. King a bag and I asked the man at the station. He told me, "go right after that man. He lives in the house just next to  10 . "

下列运河中，作为南北美洲分界线的是（　　）

高血压患者在运动时一定要量力而行，并遵循以下三个原则：一是____，运动频率最好是每周4—5次，每次持续40分钟以上；二是在运动前后要进行充分的热身和放松；三是____，过于轻松的运动，不能达到锻炼心肺功能的效果，____，又容易诱发心脏不适。