系统误差也称可测误差,是检验操作过程中由某一固定原因引起的误差,不是产生系统误差的原因是()
A.方法误差
B.仪器误差
C.试剂误差
D.过失误差
参考答案:D
— Has Sam finished his homework today, Anne?
— I have no idea. But he ________ it this morning. [ ]
A .did
B. had done
C. was doing
D. had done
当1号油箱加满油时,加油活门位置指示灯()
A.亮
B.灭
C.无指示
D.闪亮