从结构上讲柠檬酸是一种三羧酸类化合物,并因此而与其他( )有相似的物理和化学性质。加热至175°C时它会分解产生( )和水,剩余一些白色晶体。
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2 Conversation: Why Don’t We Have Lunch Together?A. Listen to the following conversation and then decidewhether each of the statements below is true (T ) orfalse (F ).[音频][音频]_____ 1. Jill and Sue have known each other for some time._____ 2.They are very surprised to run into each other.______3. Jill is teaching in Hong Kong now.______ 4. Both Jill and Sue are single.______ 5. Jill gives Sue her card.
B. Listen to the passage again and then complete the followingsentences.[音频]
CRH2型动车组的辅助供电系统由牵引变压器辅助绕组、____、蓄电池、辅助及控制用电设备、地面电源等几部分组成。