题干

下列说法中,错误的是(  )

A:在四冲程内燃机中,只有做功冲程对外做功

B:热机排出的废气、产生的噪声,都会污染环境

C:因为汽油的热值比柴油的高,所以汽油机的效率比柴油机高、对环境污染小

D:内燃机中是靠连杆和曲轴将活塞的往复运动变成曲轴的转动的

上一题 下一题 0.0难度 选择题 更新时间:2019-07-15 08:09:32

答案(点此获取答案解析)

C

同类题3

根据短文理解,选择正确答案。

    Anny was a five-year-old girl. One day when she and her mother were in a department store(百货商店), Anny saw a plastic pearl necklace (珍珠项链). What a beautiful necklace! She wanted it very much, so she begged(乞求)her mother to buy it for her. The mother said, “Well, I can buy you the necklace, but when we get home, we should discuss what you can do to pay for it. Can we do that?” Anny agreed with much happiness, and she got the necklace.

    How much Anny loved the necklace! She wore it everywhere and every minute. Anny also did part - time jobs to make pocket money. She worked very hard. Soon she succeeded in paying off the price for the necklace.

    Anny's daddy knew how she tried her best to get the necklace. He also knew how much Anny cared about it. One night, he asked Anny if she loved him. “Sure, Daddy.” the little girl said. “Then how about giving me your necklace?” “Oh, no, Daddy! Not my necklace!” Anny cried. “Oh, dear, it's fine.” her father gave her a kiss.

    Several days later, Anny went to her daddy, with her lips(嘴唇) trembling(颤抖). “Here, Daddy. I love you.” She held out her hand. Inside it was the plastic pearl necklace that she loved so much.

    When he saw this, Anny's father smiled with surprise. He then pulled a cute box out of his pocket. Inside the box was a real and colourful pearl necklace, which was waiting for Anny for so long.