TheSecondWorldWarmillionsofpeoplewerekilledendedin1945.A.whenB.inwhichC.which

Question

The Second World War ____ millions of people were killed ended in 1945.
A.when B.in which C.which

Answer 1

B.in which
我怕解释不清 which是代second world war 前面要＋上介词in （in the second world war）
可以看看把句子的拆开
Millions of people were killed in the Second World War.
Second World War ended in 1945
自己理解下把