a molehill 土丘
make a mountain out of a molehill 小题大做
A: Why are you so upset about this tiny mistake?
A：你为什么会对这个小错误这么生气呢？
B: I'm not, I just think you're making a mountain out of a molehill.
B：我没生气，我只是觉得你在小题大做。
1) 鼹鼠堆出的土丘
2) 比喻微不足道的小事
1. 鼹鼠丘
noun
1. A small mound of earth made by a mole.
Synonym: mound