Which of the following sentences is not written in parallel structure?
1) The director's main responsibilities are to ensure regulatory compliance, hire and train staff, and maintain a safe and nurturing environment.
2) The director's main responsibilities are ensuring regulatory compliance, hiring and training staff, and maintaining a safe and nurturing environment.
3) The director's main responsibilities are to ensure regulatory compliance, hiring and training staff, and maintaining a safe and nurturing environment.
4) The director's main responsibilities are to ensure regulatory compliance, to hire and train staff, and to maintain a safe and nurturing environment.
