李某由于骑摩托车不戴头盔，被交警发现，罚款200元。下列认识正确的是（  ）

“汽车不但要吃油，有时也要喝水”，用水冷却发动机是因为水的____大，在发动机开始工作一段时间内，水箱中水的内能会____（填“增加”或“减少”），这是通过____方式改变内能的；一台单缸四冲程汽油机的飞轮转速是1800r/min，则汽油机每秒对外做功____次.

完形填空

   Nancy is reading an e-mail from her friend Jack. She is very1 to get the e-mail. Jack writes about his school2 his weekends. Jack likes his school very much. Nancy likes her school,3 . Jack's school is very big and he likes his classroom. The4  and chairs are new. There are lots of pictures5 the wall. They clean the classroom every day.

   Jack doesn't 6to school at the weekend. He gets up7at six on Saturday. He exercises in the park for half8. Then he eats his breakfast. He helps his mother do the9. At eight he begins to do his homework. He has lunch in a fast food restaurant (快餐店). In the10, he goes shopping with his mum. Sometimes he plays computer games or chats with his friends on the Internet. He enjoys his weekends very much.

从下列实验现象的编号中，选择合适的编号填入题后的横线上

A、火焰呈淡蓝色　B、火星四射　C、耀眼白光　D、浓厚白烟　E、蓝紫色火焰

红磷在氧气中燃烧　____ 　　镁在空气中燃烧　　____ 　氢气在空气中燃烧　____ 　；

硫在氧气中燃烧　____ 　细铁丝在氧气中燃烧____