1. He is in charge of sales.
彼は販売の担当です

2. They are in charge of handling the project.
彼らはこのプロジェクトを扱う担当です

3. Who is in charge here?
ここは誰が責任者ですか？

4. The manager is in charge of training the new recruits.
マネージャーは新人研修の担当です

5. Those who are in charge make the rules.
責任者がルールを作ります。