They last employed new staff back in January. taken No new staff
They last employed new staff back in January. (taken) => No new staff …
They last employed new staff back in January. (taken) => No new staff …
Đáp án: No new staff has/ have been taken on since January.
Dịch: Lần gần đây nhất họ thuê nhân viên mới là vào tháng Giêng.