A man was traveling abroad in a small red car. One day he left the car and went shopping. When he came back, its roof was badly damaged.

    Some boys told him that an elephant had damaged it. The man did not believe them, but they took him to a circus(马戏团) which was near there. The owner of the elephant said, “I am very sorry! My elephant has a big, round, red chair. He thought that your car was his chair, and he sat on it!"

    Then he gave the man a letter, in which he said that he was sorry and that he would pay for all the damage.

    When the man got back to his own country, the customs（海关） officers wouldn't believe his story. They said, “You sold your new car while you were abroad（国外） and bought this old one!"

    It was only when the man showed them the letter from the circus man that believed him.

目前，心血管疾病已成为威胁我国人们健康的主要疾病，为了预防心血管疾病，我们在平时的饮食中应注意（   ）

下列各项对语法知识的判断与分析，正确的一项是（    ）