The pilot said he ()our vessel directly to the berth.
A. will take
B. took
C. is taking
D. would take
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氡(α衰变)半衰期为4天,经过8天后,其剩余量为()
A. 1/2
B. 1/4
C. 1/8
D. 1/16
肺灌注动态显影常应用的放射性核素显影的种类是()
A. Xe131
B. Tc99m
C. Tl201
D. Ga
E. In111
为了防止表面划痕,精密磨削选择砂轮特性为WAF()L。