下列说法正确的是（ ）
A．棉花、合成纤维和合成橡胶都属于合成材料
B．用亚硝酸钠代替食盐腌制腊肉
C．用水灭火的原理是降低可燃物的着火点
D．水银、干冰、酒精依次属于单质、氧化物、化合物
相关试题
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 |
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