制作血沉自动分析仪的血沉管的材料是（）
A.不锈钢
B.铜质
C.硬质玻璃或塑料
D.有色玻璃
E.铝质
参考答案：C
用描述法表示二元一次方程x-y=0的解集为______．
MacDonald who had spent much of his time graduating from college backpacking round Europe,decided last year to settle down.
A．when
B．while
C．since
D．before
