This is perhaps the same car which ran her over while she was returning from school.

The most appropriate phrase to replace the given phrase in bold to make the sentence grammatically correct is “that ran her over while she was”. It is to be noted that we will use ’that’ in place of ’which’ after ’the same’ if the verb is clear. Here the word ’was’ shows that the verb is clear. Hence, considering the given rationale option 1 becomes the most suitable answer choice.