一A child’s family background brings him or her a bright future．

一Not really . A study shows that reading for pleasure plays a more important _________.

A．part           B．game           C．joke

尿毒症患者以碳酸氢钠静脉滴入纠正代谢性酸中毒时发生手足搐搦机制是（）

A.低钾血症

B.高钠血症继发脑水肿

C.血中钙总量降低

D.血中结合钙降低

E.血中游离钙降低