吗 ma is used to form simple questions which can be answered with yes or no.
In order to form a question with 吗 ma (= particle), 吗 ma is simply added at the end of a statement.
Structure of a Statement
|China||very, quite||big, old, main||。|
|China is big.|
Structure of a Question
|China||very, quite||big, old, main||particle||？|
|Is China big?|