题干
根据句意，补全对话。
— What are the students ____?
— They are ____ for their parents.
答案(点此获取答案解析）
doing,singing
根据句意，补全对话。
— What are the students ____?
— They are ____ for their parents.
元素，其中甲、乙两元素原子的最外层电子数分别是次外层电子数的2倍和3倍，丙元素原子K层和M层电子数之和与L层的电子数相同．下列判断不正确的是（ ）
