设NA代表阿伏加德罗常数，下列说法正确的是（ ）
A．23g金属钠变为钠离子时得到的电子数为NA
B．标准状况下，18g水所含的电子数目为10NA
C．标准状况下，11.2L氦气所含的原子数目为NA
D．标准状况下，2.24LN2和O2的混合气体所含原子数为0.1NA
A.23g金属钠变为钠离子时失去电子，而不是得到电子，故A错误；
B．n=
=1mol，含有10mol电子，数目为10NA，故B正确；18g 18g/mol
C．He为单原子分子，则标准状况下，11.2L氦气所含的原子数目为0.5NA，故C错误；
D．标准状况下，2.24LN2和O2的混合气体为0.1mol，二者都是双原子分子，则所含原子数为0.2NA，故D错误．
故选B．
Directions: There are 4 passages in this part. Each of the passages is followed by 5 questions or unfinished statements. For each of them there are 4 choices marked A, B, C and D. Choose the best one and mark your answer on the ANSWER SHEET with a single line through the center.
Passage One
| Andrea had never seen an old lady hitchhiking before. However, the weather and the coming darkness made her feel sorry for the lady. The old lady had some difficulty in climbing through the car door, and pushed her big brown canvas shopping bag down onto the floor under her feet. She said to Andrea, in a voice that was almost a whisper, "Thank you dear - I’m just going to Brock Bourne" Something in the way the lady spoke, and the way she never turned her head, made Andrea uneasy about this strange hitchhiker. She didn’t know why, but she felt instinctively that there was something wrong, something old, and something dangerous. But how could an old lady be dangerous It was absurd. Careful not to turn her head, Andrea look sideways at her passenger. She studied the hat, the dirty collar of the dress, the shapeless body, and the arms with their thick black hairs. Thick black hairs Hairy arms Andrea’s blood froze. This wasn’t a woman. It was a man. At first, she didn’t know what to do. Then suddenly, an idea came into her racing, terrified brain. Swinging the wheel suddenly, she threw the car into a skid, and brought it to a halt. "My god!" she shouted. "A child! Did you see the child I think I hit her. " The "old lady" was clearly shaken by the sudden skid. "I didn’t see anything dear," she said. "I don’t think you hit anything. " "I am sure it was a child!" insisted Andrea. "Could you just get out and have a look Just see if there is anything on the road" she held her breath. Would her plan work It did. The passenger slowly climbed out to investigate. As soon as in front of her vehicle, Andrea gunned the engine and accelerated madly away, and soon she had put a good three miles between herself and the awful hitchhiker. It was only then that she thought about the bag lying on the floor in front of her. Maybe the bag would provide some information about the real identity about the man. Pulling into the side of the road, Andrea opened the heavy bag curiously. It contained only one item — a small hand axe, with a razor-sharp blade. The axe, and the inside of the bag, were covered with the dark red stains of dried blood. Andrea began to scream. |
Andrea allowed the hitchhiker to take a ride in her car, mainly because ______.
A．the hitchhiker was an old woman
B．she was curious about the old lady
C．the lady had a heavy bag
D．she knew the old lady