where are you going on holiday?
应划分为where are you going | on holiday
on holiday是一个固定搭配表示度假
go在此句中的变形是going 是因为be going
这句话是以现在进行时表将来
而do及其变型did 后跟的是动词原形
所以应为where did you go on holiday

你语法掌握得不是很好 基础不大好
建议你看到一个问句时试着先把它变为陈述句再判断动词形态等
如where did you go 陈述句即为 you go where
where are you going 即为 you are going were
that‘s it