女孩，6个月，呕吐5天，大便8～10次/天，蛋花汤样，量多．近2天来未吃奶，今日无尿。检查：体重6kg，体温38.2，呼吸40次/分，意识蠓咙，哭无泪，口唇樱红色，前囟及眼窝深凹。右侧顶部有轻度颅骨软化，皮肤弹性极差，四肢厥冷，脉细弱，心率140次/分，心音略钝，两肺(－)，腹软不胀．血清钠134mmol/ L，血钾4.1mmol/L，HCO₃ˉ9mmol/L。

经输入碳酸氢钠后，呼吸平静，已排尿，脱水症状不明显，但下午突然全身抽搐2次，每次约持续1分钟，自行缓解，抽搐后患儿神志清楚，引起抽搐最可能的原因为

A．低血糖

B．低血钙

C．低血镁

D．酸中毒

E．低血钾

By using MP3，a 600M-byte music CD can be (71) to 50M bytes or less．It can be streamed(downloaded in chunks)so that you can begin listening to the opening bars while the (72) ofthe life arrives in the background。And most important，MP3 music files retain good listening (73) that (74) compression schemes lacked．That (75) of features makes accessing anddistributing music on the Web practical for the first time．

A．earlier

B．front

C．later

D．backward