【题目】Happiness is a butterfly, which, when pursued, is always just beyond your grasp, but ________, if you will sit down quietly, may alight upon you.
A. that B. which C. one D. whose
在线课程【答案】B
【解析】
试题分析：考查非限制性定语从句。句意：幸福是一只蝴蝶,你要追逐它的时候,总是追不到,但是如果你悄悄的坐下来,它也许会飞落到你身上。a butterfly做先行词，故选B。