It takes about five minutes to walk . . . . . . . . the bridge. A. over B. to C. at D. till

The correct answer is A. over.

The preposition “over” is used to indicate movement from one side of something to the other. In this case, the speaker is saying that it takes about five minutes to walk from one side of the bridge to the other.

The other options are not correct because they do not indicate movement from one side of something to the other. The preposition “to” is used to indicate movement towards a destination. The preposition “at” is used to indicate a location. The preposition “till” is used to indicate a point in time.

Here are some examples of how the other options could be used in a sentence:

• I walked to the bridge.
• The bridge is at the end of the street.
• I will wait till you cross the bridge.