A:充分不必要条件
B:必要不充分条件
C:充要条件
D:既不充分也不必要条件
则:
设实数数列{an},{bn}分别为等差数列与等比数列,且a1=b1=4,a4=b4=1,则以下结论正确的是( )
I ______ have worried before I came to the new school, for my classmates here are very friendly to me.
读世界海洋与陆地分布图,回答下列问题