用绳子量桥高。在桥上将绳子4折垂至水面,余3米,把绳剪去6米,3折后,余4米,求桥高是多少米
A.36
B.12
C.9
D.6
参考答案:D
万级的计数单位有______,亿级的数位有______.
婴儿基础代谢每日需要热能为
A.168kJ/kg(40kcal/k
B.189kJ/kg(45kcal/k
C.230kJ/kg(55kcal/k
D.210kJ/kg(50kcal/k
E.252kJ/kg(60kcal/k