连词成句。

1. are, they, sightseeing, who, going, with

    ____________________________?

2. wants, vacation, David, exciting, an

    ____________________________.

3. Peter, taking, is, long, a, vacation, summer, this

    ____________________________.

4. about, plan, some, ask, can, your, I, vacation, you, questions

    ____________________________?

5. He, going, his, house, is cousin's to

    ____________________________.

当系统中的变频器是以三相六脉动全波整流为主时，根据公式谐波次数K=6N±1，谐波以5、7次为主，通常采用并联式5次和7次单调谐滤波器。