If you have to choose from on / in /at then in is the best UK English, US English users may have a different answer.
I prefer:
I was walking along the street.
I was walking down / up the street.
She fell over in the street.
The accident happened in the main street.
The children were playing in the street. (dangerous if there is traffic)
Answer the questions while listening to the audio.
Answer the questions as you listen to the audio.
Make sentences using these relative clauses correctly. (You supply the clauses to be used)
Write sentences which include a relative clause. (Student must create the whole sentence)