将一定量的乙醇（C2H6O）和氧气置于一个封闭的容器中引燃，测得反应前后各物质的质量如下表：
| 物质 |
乙醇 |
氧气 |
水 |
二氧化碳 |
X |
| 反应前质量/g |
4.6 |
8．0 |
0 |
0 |
0 |
| 反应后质量/g |
0 |
0 |
5．4 |
4．4 |
a |
下列判断正确的是 （ ）
A．表中a的值为2.6
B．X一定是该反应的催化剂
C．X可能含有氢元素
D．若起始时氧气的质量是9.6g，则无X生成
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 |
--- 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 |