Fill in the blanks with the most appropriate option:-

So quickly did we walk that we reached the station ….. time.

in

The correct option to fill in the blanks is in.

The sentence is about the speaker's quick walk to the station. The preposition "in" is used to indicate a period of time. It is the most appropriate preposition to use in this context, as it describes the fact that the speaker reached the station in a short period of time.

The other options are not as appropriate:

• On is used to indicate a point in time. It is not as appropriate as "in", as it does not convey the same sense of duration.
• At is used to indicate a specific location. It is not as appropriate as "in", as it does not convey the same sense of speed or urgency.
• For is used to indicate a purpose or reason. It is not as appropriate as "in", as it does not convey the same sense of swiftness.