A hinge joint is______ permits the forward and backward movement of a door.
A. what
B. that
C. which
D. where
查看答案
起跑时重心在哪？
A. 重心在身体靠前
B. 重心在身体靠后
C. 重心在身体中间
起跑的蹬地方向在哪？
A. 向前推
B. 向后推
C. 侧前方
起跑的难点是？
A. 起跑时保持轮子与地面垂直
B. 起跑时保持两脚尖向前
C. 蹬地时轮子向后方蹬地
Fossile records indicate______ existing in the past have become extinct.
A. that many species of organisms
B. many species of organisms that are
C. many species of organism are
D. there are many organisms
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