化学老师出了一条谜语：看不见，摸不着，越往高处越稀少，生命活动离不了——打一物质。你猜谜底是（ ）
| A．N2 | B．O2 | C．H2 | D．CO2 |
--- I've just got a postcard from my pen friend.
--- Let me have a look
. Wow.nice card!
| A． | What | B． | What a | C． | How | D． | Why |
--- What is your favourite sport?
--- Swimming, I think. It's of all.
| A． | earsier | B． | more difficult | C． | the most interesting | D． | the most boring |
---I use your ruler, Lingling?
--- Sure. Here you are.
| A． | May | B． | Would | C． | Need | D． | Must |
--- Do you like watching TV?
---Yes, I. But only after I finish my homework.
| A． | am | B． | do | C． | does | D． | did |
Li Yan is my best friend. She comes a small village.
| A． | B． | C． | D． |