患儿男，5岁。因频繁发作性发呆1个月就诊，脑电图示全脑同步3Hz棘-慢复合波爆发，过度换气可诱发，其首选抗癫痫药物是()

A.丙戊酸钠

B.氯硝西泮

C.拉莫三嗪

D.托吡酯

E.卡马西平

－______milk do you need to buy?

－Two cartons.

A．How many

B．How long

C．How much

D．How often