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Dear Mike,

    We got your letter yesterday. Yes, we can visit you at Christmas. We thought to spend(度) Christmas

at home, but now we are going to be with you. Jack will not be in school then.

    The weather in Chicago is cold, but it doesn't matter. Sometimes we like the snow.

    We got our plane tickets. We will get to your city on the 18 th. We will stay with you for two weeks. Is

that all right with you?

    We'll take our favourite recipes(食谱), so we can have a nice Christmas dinner.

    See you soon.

                                                                                                                             Love

                                                                                                                       Mum and Dad

根据短文内容用适当的单词完成下面句子:

1. In Chicago, it is __________ now.

2. Mike has a brother called __________. He is in school now.

3. Mike's parents will go to his city by __________.

4. His parents will come back on __________ 31st.

5. Mike and his parents will __________ a nice dinner on Christmas Day.

液压传动系统的功率与系统的压力和流量有什么关系？