Under what conditions can you pass another car?

Answer: B — When the passing lane is free

Passing is legally allowed when there is a designated passing lane, which is the lane on the opposite side of the road from the one you are driving in. Passing should be done with caution and only when it is safe to do so. Option A is incorrect because other cars may be approaching from the opposite direction and it would not be safe to pass. Option C is incorrect because passing should not be done at any time, only when it is safe and legal to do so. Option D is incorrect because there are certain circumstances, such as a designated passing lane, when passing is permitted. Therefore, the correct answer is B.