Choose the sentence that has the incorrect preposition in it:

The correct option is: The train is running off time.

Let's analyze why this sentence is grammatically incorrect by breaking down the usage of prepositions step-by-step:

1. Understanding the error in the first sentence:
The phrase "running off time" is incorrect. In English, when we want to express that a train, bus, or schedule is not arriving or departing at the scheduled time, we use the preposition behind. Therefore, the correct idiomatic expression is "running behind time" (or simply "running late"). The preposition "off" does not correctly convey this temporal delay.

2. Analyzing the correct options to verify:
• "It has been five years since I have seen my mother." — The preposition/conjunction since is used correctly here to indicate the starting point of a period of time that continues to the present.
• "Sheela left for the station an hour ago." — The preposition for is used correctly after "left" to indicate direction or destination.
• "Vineet studied till 1am for his upcoming exam." — The preposition till is used correctly to indicate the limit of time up to which the action of studying continued.