疑問符

Use the question mark at the end of all direct questions.

直接疑問文の終わりに疑問符をつけます。

間接疑問文には、疑問符を使ってはいけません。

長い疑問文にも疑問符は必要です。

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?

文章内に疑問符が表れる場合があります。

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.