Homework : Choose the best answer

1. Her teaching style in similar ( at/ with/ to / in) that of most other teachers.
=> My answer : to   CORRECT :)     similar+to
2.We want people to be aware ( with/ in / to/ of) problem of pollution.
=> My answer : of     CORRECT :)   aware+of
3. Police officers have to wear uniform when they are ( on/ in / of/ off ) duty.
=> My answer: in      Police officers can be ON DUTY or OFF DUTY. But they only wear uniforms ON duty. ;)
4.The telephone and the doorbell rang ( on/ in/ at ) the same time.
=> My answer: at    CORRECT  :)  at + the same time
Can you cure correct me and explain if I am wrong?
Thank you so much ^^

Mostly very well done. Keep practising! ^_^