区别尿血与血淋的关键是（）。
A.尿色的深浅
B.尿中有无红细胞
C.尿时痛与不痛
D.是否伴有全身症状
E.是否伴有水肿
参考答案：C
.
By around 900 AD,there were many places in Northern Europe______the Vikings chose to live.
A．in which
B．when
C．which
D．at which
机油中混入水会造成（）。
A.机油压力过低
B.机油压力过高
C.柴油机过热
D.柴油机飞车
