如: I have no idea which one I should buy (同位语从句) I have no idea, which one I should buy (非限定性定语从句)而且直接把中间的逗号去掉,变成限定性定语从句好像从意思上也说的通?非限定性定语从句对“idea”起补充说明作用,同位语从句对“idea”也是起说明的作用,好像没多大区别?