Option 1 -> "minds had crossed" is not a standard English idiom or phrase.
Option 2 -> "footpaths had crossed" is not a recognized expression in English.
Option 3 -> "paths had crossed" is a common English idiom meaning two people met or encountered each other.
Option 4 -> "cars had crossed" is not a standard idiom or appropriate phrase in this context.
Hence, Option 3: paths had crossed -> This is the correct idiomatic expression used to describe when two people meet or encounter each other, often by chance or coincidence. Since both were in Chennai at the same time, their paths (routes/journeys through life) likely crossed, meaning they probably met or came across each other -> correct