下列变化中，属于物理变化的是（ ）
A．光合作用
B．煤的燃烧
C．冰雪融化
D．菜刀生锈
A、光合作用的过程中植物吸收二氧化碳，释放出氧气，有新物质生成，属于化学变化．
B、煤的燃烧的过程中有新物质二氧化碳、二氧化硫等生成，属于化学变化．
C、冰雪融化的过程中只是状态发生改变，没有新物质生成，属于物理变化．
D、菜刀生锈的过程中有新物质铁锈生成，属于化学变化．
故选C．
| 完形填空。 | |||
| Recently, how teachers should criticize (批评) students __1__ reported in the news. It is because of a new __2__ from the Ministry of Education. It says that the head teachers have rights to criticize their students "in a proper way". Many teachers welcome the rule. They say the move will help teachers __3__ educate students. "Today's teachers are afraid it will hurt students' pride," said Ms Yang, "Most of the students are single children, and their __4__ are very protective." Yang once criticized two boy students who had fought in her class. __5__ next day, the boys' parents went to the headmaster and said that Yang had been too hard on their boys. Since then, she has been very careful __6__ criticizing students. But some teachers think the rule is too general (宽泛的). What is a "proper manner"? They ask. Here is __7__ students have to say. Wen Wen is a Junior 2 student __8__ Changsha. She says that when her teachers criticize students, they do not use harsh (刺耳的) words. Most of her classmates __9__ this kind of criticism. Guo Xiaoyu, a __10__ Beijing student thinks it is better to criticize a student in private (私下)."I don't like teachers criticizing me in front of the whole class. I lose face," she said. | |||
| ( ) 1. A.have been ( ) 2. A.idea ( ) 3. A.well ( ) 4. A.parents ( ) 5．A．A ( ) 6. A.with ( ) 7. A.that ( ) 8. A．in ( ) 9. A.like ( ) 10.A.15 years old | B. has been B. plan B. good B. teachers B．The B. to B. when B．at B. accept B. 15-year-old | C. have C. rule C. better C. friends C．／ C. for C. what C．on C. mind C. 15 year old | D. was D. reason D. easier D. classmates D．One D. about D. how D．of D. reply D.15-years-old |