在冬天，装有一定量水的热水瓶过了一段时间后，软木塞不易拨出，这主要是由于（ ）
A．瓶内气压大于大气压
B．瓶内气压小于大气压
C．瓶塞遇冷收缩
D．塞子与瓶口间的摩擦力增大
A、瓶内的水蒸气液化后，瓶内气体减少，气压降低，小于外界大气压．而不是大于外界大气压．故A错误．
B、由于瓶内水蒸气的液化造成内部气压小于外界大气压．故B正确．
C、瓶塞遇冷收缩，只会造成更容易拔出软木塞．而不是不易拔出．故C错误．
D、若塞子与瓶口间的摩擦力增大，确实不易拔出软木塞，但在这个过程中，影响软木塞与瓶口间的摩擦力大小的因素：两者之间的压力大小、接触面的粗糙程度都没有变化，所以摩擦力不会变化．故D错误．
故选B
| 情景匹配。 | |
| A: What're you going to do this weekend? B: Oh. I'm planning to have a party. 1.________ A: Thank you. 2.________ What time will it start? B: At three o'clock. We will have it at my place. A: But I don't know where you live. 3.________ B: Oh, it's easy to find my home. My home is on Garden Street. A: I don't know the way to Garden Street. Where is it? B: 4.________ Get off at the bus stop. And I will wait for you there at 2:30 p.m. A: OK. 5._________ See you. B: See you.
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