People in North China eat noodles as their main food ___ people in the south eat rice.
A:as
B:while
C:when
选择最佳应答语( )
若向量a→=(1,λ,2),b→=(2,﹣1,2).a→,b→夹角的余弦值是89,则λ的值为( )
下列句子中加下划线的词语运用不恰当的一项是____________