（）地球大气的演化经历了原始大气、次生大气和现代大气三个阶段，次生大气中部分成分的微观示意图如下：
一定条件下，3．4g甲物质和4．8g氧气恰好完全反应，生成5．4g乙物质和另一种物质X，下列判断不正确的是
| A．物质甲的化学式是NH3 |
| B．物质X的质量为2．8g |
| C．物质X中含两种元素 |
| D．该反应化学方程式中物质X与O2的化学计量数之比为2:3 |
This is my beautiful school is near the famous library.
| A． | where | B． | which | C． | who | D． | when |
--- Can you tell me ______ on the Internet? --- OK, mum.
| A． | how can I use QQ | B． | where can I use QQ |
| C． | how I can use QQ | D． | whether can I use QQ |
Thousands of houses _______ by the floods in Guangxi last month.
| A． | destroy | B． | destroyed | C． | have destroyed | D． | were destroyed |
more, and you'll improve your spoken English.
| A． | Speak | B． | Speaks | C． | Speaking | D． | To speak |
--- 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 |