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
The early years of the United State government were characterized by a debte concerning______ or indiviudal states should have more power.
A. whether the federal government
B. either the federal government
C. that the federal government
D. the federal government
微信支付 
支付宝支付