题目

Tom,as well as his parents, _(watch) TV at present. 答案：【1】is watching下列各组物质的分类，正确的是（       ）A．同位素：金刚石、石墨B．非极性分子：H2O、NH3C．同系物：－OH、－CH2OHD．同分异构体：HCOOCH3、HOCH2CHO