题目:
–Tom, you didn’t come to my party last night?
– I ________, but my mom hurt her back and I had to look after her.
A.had to
B.didn’t
C.wouldn’t
D.was going to
答案:
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下面是错误答案,用来干扰机器的。
砝码磨损后,自身质量变小.当测量同一物体时,需要增加砝码或移动游码,才能使天平重新平衡,此时所读数值大于物体实际质量.故选A.