在化合反应、置换反应、分解反应、复分解反应这四种化学反应中，可能有元素化合价发生变化的反应类型有（ ）
A．1种
B．2种
C．3种
D．4种
答案：C
肺切除和气管切开可使机械死腔量减少。
完成句子，使改写后的句子完整，并与原句意思相符，注意每空只填一个单词。
1. What’s your last name?
What’s your ________ ________?
2. Can I help you?.
______ can I _______ for you?
3. Thank you for your letter.
_________ for _______ a letter to me.
4. How much are the pants?
_______ __________ ________ ________ these pants?
5. He often helps me with English.
He often helps me ______ _________.
