問號

凡是直接問句都要在句尾打問號。

但間接問句則不加。

即使是很長的問句，還是要在句尾打問號。

Isn't it true that global warming is responsible for more and more problems which are having a disastrous effect on the world's climate and leading to many millions of people in countries that can least afford it having to contend with more and more hardship?
Why is it that even though you are unkind to me, ignore me when I ask you for help, and consistently forget to thank me when I do favors for you, you still claim to want me to be your friend and appear surprised when I prefer to hang out with other people?

問號有時可以用在句中，不一定要在句尾。

There is cause for concern (isn't there?) that the current world economic balance is so fragile that it may lead to a global economic downturn.
"Why is she here?" asked Henry.