The correct option is
A drive
In order to fill in the blank with the most suitable form of infinitive, we need to understand the meaning and usage of 'rather than'. 'Rather than' means the same as 'would rather', which means 'instead of' or preferring someone or something over the other. If 'rather than' is used in a passive (voice) sentence, we use the word 'to' along with the verb. Generally, we in an active sentence, we do not use 'to' with the verb. The verbs without the marker 'to', are called the bare infinitives.As the given sentence is in active voice, we will use the bare infinitive here.
Option B - 'Drove' is the past form of the verb 'drive'. As we need the bare infinitive (original form of the verb), we can't use 'drove' here. Hence, option B is incorrect.
Option C - 'Drives' is the third person form of the verb 'drive'. As 'drives' is not the original form of the verb (bare infinitive), we can't use it here. Hence, option C is incorrect.
Option D - 'To drive' can't be used here, as the verb is in its original form with the marker 'to'. As the sentence is in active voice, we can't use the infinitive with 'to' here. Hence, option D is incorrect.
Option A - 'Drive' is a verb in its original form and is a bare infinitive. Also, it supports the tense of the sentence. Hence, option A is the correct answer.
'Sometimes I walk rather than drive.'