The interrogative particle 吗
When the interrogative particle 吗 (ma) is added at the end of a declarative sentence, it becomes a question.
Example 1:
你认识她。 You know her.
你认识她吗？ Do you know her?
Example 2:
他是医生。 He is a doctor.
他是医生吗？ Is he a doctor?
The interrogative particle 吗