His waltzes _____ him famous all over Europe.[ ]
A. kept
B. made
C. felt
答案:B
设向量a=(1,2m),b=(m+1,1),c=(2,m).若(a+c)⊥b,则|a|=________.
门卫人员要精神饱满,站姿端正,真诚微笑,在大堂内执行()任务。
A.安全保卫
B.站岗放哨
C.敬老爱幼
D.值班值日