Can you explain why you were so late?

你能解释一下为什么迟到了吗?

How come it has taken you so long to reply to my email?

你怎么这么久才回复我的邮件?

I don’t understand why you never finished the work on time.

我不明白你为什么从来没有按时完成工作。

Do you expect me to believe you did this by yourself?

你以为我会相信这是你自己干的吗?