把正方形ABCD对折，得到折痕MN（如图①），展开后把正方形ABCD沿CE折叠，使点B落在MN上的点B’处，连结B’D(如图②)。
试求∠BCB’及∠ADB’的度数。
   

用所给词的适当形式填空
（1）I’d like to visit Beijing because the people there are very ____  (friend).
（2）The oranges come from ____ (south) China.
（3）What other____  (language) do you like? 
（4）There ____  (be) lots of meat in the ice box.
（5）How many ____  (box) of apples would you like? 

下列现象是由地球自转产生的是（ ）