问题
选择题
There are fewer teaching positions left in big cities, ______ at the same time there are shortages of teachers in small towns．
A．or
B．and
C．so
D．for
答案
答案：B
考查连词。or 表选择关系；and表并列关系；so和for表因果关系。句子前后是并列关系，所以选B。