引起氟斑牙的主要因素是

A．婴儿期高热性疾病

B．母亲妊娠期的疾病

C．发育期缺微量元素

D．人体氟摄入量过低

E．人体氟摄入量过高

Harry started a 6-mile hike with a full 10-cup canteen of water and finished the hike in 2 hours with 1 cup of water remaining in the canteen. If the canteen leaked at the rate of 1 cup per hour and Harry drank 3 cups of water during the last mile, how many cups did he drink per mil during the first 5 miles of the hike ？（）

A.A

B.B

C.C

D.D

E.E