All of us must practice English after class .[ ]
A. saying
B. speaking
C. say
D. speak
答案:B
胃十二指肠溃疡穿孔可出现:
A.血栓性浅静脉炎B.血栓性深静脉炎C.游走性浅静脉炎D.血栓闭塞性脉管炎E.动脉硬化闭塞症
示值误差是相对误差的简便实用形式,在多档或连续刻度的仪表中广泛应用。 ( )