Question

一道英语填空题？

However,after a year or so （）they became more serious about their wok.

Answer 1

应该填during which，表示在那一年里

However，after a year or so during which they became more serious about their work.

意思：然而，大约一年之后，这一年间它们对于自己的工作更加认真。

Answer 2

in which (一般来说介词加关系代词等于关系副词，in which引导定从，指代in a year or so，在这里应该是时间状语)