在细胞有丝分裂过程中，染色体、染色单体、DNA分子三者数量之比是 1 ：2：2 时，该细胞所处的时期是

如图，正方形ABCD中，AB=6，点E在边CD上，且CD=3DE．将△ADE沿AE对折至△AFE，延长EF交边BC于点G，连结AG、CF．下列结论：①△ABG≌△AFG；②∠EAG=45°；③BG=GC；④AG∥CF．其中正确结论的个数是（   ）

磁感应强度的单位是（）

先通读下面的短文，掌握其大意，然后从A、B、C、D四个选项中选择可以填入空白处的最佳答案。

Hi Lily,

    How are you?Thanks for your last e-mail．You want to1about my school clubs，right?Well,it's time for my friends and I to2the school clubs now．There are many clubs in my school，3the English club，the art club，the music club and the sports club．I have two good4，Jack and Lisa．We all want to join the school clubs．

    I want to join the5club，because I can play the guitar．I6speak English well，but I also want to join the English club．Jack likes sports．7can play soccer and basketball．He wants to join the sports club．He can play the guitar,too．8he doesn't want to join the music club．Lisa likes9．She wants to join the art club．She also speaks English very well．I think she can be in the10club．

    Are there many clubs in your school?What club are you in?

    Please write to me．

Yours．

Lucy