下列化学符号，既能表示一种元素，又能表示一个原子，还能表示一种物质（ ）
A．O3
B．Cu
C．H2O
D．KMnO4
A、O3，化学式，表示臭氧这种物质，表示构成臭氧的一个臭氧分子；
B、Cu，元素符号，表示铜元素，表示铜元素的一个铜原子；化学式，表示金属铜这种物质；
C、H2O，化学式，表示水这种物质，表示构成水的一个水分子；
D、KMnO4，化学式，表示高锰酸钾这种物质．
故选B
| 阅读理解。 | ||||
| Mr and Mrs Brown have two children, Mike and Liz. The whole family are all busy, so they often leave notes for each other. Read these four notes of today and answer the following questions.
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| 1. When will Liz be back home? | ||||
[ ] | ||||
| A. At 3:30 p.m. B. At 4:00 p.m. C. At 5:00 p.m. D. At 9:00 p.m. | ||||
| 2. Who should walk the dog today? | ||||
[ ] | ||||
A. Mike. | ||||
| 3. What's Mike probably doing at 6:50 p.m? | ||||
[ ] | ||||
| A. Practicing football. B. Going to Donna's house. C. Playing tennis. D. Doing his homework. | ||||
| 4. Where can Mike find his tennis shoes? | ||||
[ ] | ||||
| A. In his bedroom. B. Outside the back door. C. In the living room. D. At Donna's house. | ||||
| 5. According to the notes, Teddy is . | ||||
[ ] | ||||
| A. Mike's mother B. Mike's brother C. Mike's football coach D. the dog in the family |