设NA为阿伏加德罗常数，下列说法中正确的是
| A．标准状况下，22.4 L水中含分子数为NA |
| B．23g金属Na与1L0.1mol/L的盐酸溶液反应，生成0.1NA个H2 |
| C．标准状况下，2.24L18O2中所含中子的数目为NA |
| D．14g分子式为CnH2n的(n≥2)链烃中含有的C=C的数目一定为NA/n |
It is often ______ that human beings are naturally equipped to speak.
| A．said | B．to say | C．saying | D．being said |
I can’t leave. She told me that I ______ stay here until she comes back.
| A．can | B．must | C．will | D．may |
—— Do you mind my opening the window? It’s a bit hot in here.
—— ______ , as a matter of fact
| A．Go ahead | B．Yes, my pleasure |
C．Yes, I do | D．Come on |
It’s high time you had your hair cut ; it’s getting _______ . 
| A．too much long | B．much too long |
C．long too much | D．too long much |
My friend showed me round the town, ______ was very kind of him. 
| A．which | B．that | C．where | D．it |