the 'why' questions

The WHY question requires a reason for its answer (just as a WHEN question requires information related to time and a WHERE question requires information related to place)

In the English language, there are certain words which show cause-and-effect and hence they will be useful in helping you answer the WHY question.
Examples:

He was late because he missed the bus
as
since
for

He missed the bus so he was late
therefore
hence
thus
as a result

However, cause and effect can be indicated in other ways, as you can easily see from the following examples:

1. Having lost all his money, he had no choice but to seek help from his relatives.
Why did he go to his relatives for help?
Because he had lost all his money.
2. It was an impossibly hot month. The shops selling fans reported brisk sales.
Why were fans selling so well?
Because it was an extremely hot month.
3. The experience, occurring at a time when she was still recovering from the loss of her parents, left her emotionally scarred for life.
Why did the experience have such a lasting effect on her?
Because it happened when she was still recovering from the loss of her parents.