forty-five. I cannot understand (that)…
45. 我不明白……
I cannot understand why you made such a silly decision.
我不明白你为什么作出这样一个愚蠢的决定。
I cannot understand why you care for her so much.
我不明白你为什么那么在乎她。
I cannot understand how you could overlook such an important man.
我不明白你为什么会忽略这么重要的一个人物。
I cannot understand why you left without telling any of your friends.
我不明白你为什么不跟你任何一个朋友说一声就离开了。
I cannot understand why he betrayed his country.
我不明白他为什么要叛国。