力学基本训练实验中涉及到的仪器有毫米尺、螺旋测微计、()、天平,以及显微镜。
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使用游标卡尺和螺旋测微计测量物体前,应先确定测量仪器是否有()误差。
Tom as well as two of his classmates________ invited to the party.
A. was
B. were
C. have been
D. are
The Olympic games ________ held every four years.
A. is
B. was
C. were
D. are
Three-fourths of the homework________ been finished today.
A. will
B. /
C. have
D. has