题目

Sleepwalking（梦游） is when your child gets out of bed and walks around as if he’s awake, but he’s actually asleep. Sleepwalking doesn’t hurt your child, and it usually disappears when the kid grows up. Sleepwalking happens during deep sleep. Your child might get out of bed and walk around as if he’s awake, but he won’trespond normally to you or anything around him. This may make you upset. But try not to worry—your child is OK. In fact, sleepwalking is quite common. 7% to 15% of children sleepwalk, and it doesn’t usually mean that there’s anything wrong with them. Child重铬酸钾（K2Cr2O7）可用于测定酒驾中的酒精（C2H5OH）含量。下列说法正确的是（ ）A. K2Cr2O7中铬元素的化合价为+7B. C2H5OH中氢元素的质量分数最小C. K2Cr2O7属于氧化物D. C2H5OH中C．H．O的原子个数比为2：5：1