1. The interrogative sentence with “吗“
The particle “吗” indicate an interrogative mood. When “吗“ is added at the end of a declarative sentence, the declarative sentence turns into a question. For example:
他是美国人。他是美国人吗？
她是老师。她是老师吗？
2. The interrogative particle “呢“
The interrogative particle “呢“ is used after a noun or pronoun, forming a question about the situation mentioned previously. The commonly used sentence pattern is A……。B呢？（A… What about B?）For example:
我是中国人。你呢？
小明在家里。他妈妈呢？
3. The Modal particle “吧” used at the end of a sentence to indicate consultation, a suggestion, request or command.
今天下雨了，我们明天再去吧。
他现在很忙。下午再打电话吧。
When used at the end of an imperative sentence, the modal particle “吧” indicates a suggestion or command with a softened mood.
4. The modal particle “啊”
The modal particle“啊” is used at the end of a declarative sentence to set the mood。For example:
A：他是美国人吗？
B: 是啊。他是加州人。