The correct answer is C. with.
The preposition “with” is used to indicate a relationship between two or more people or things. In this case, the speaker is saying that the listener is friendly with the Tans. This means that the listener has a positive relationship with the Tans, and they enjoy spending time together.
The other options are not as appropriate in this context. The preposition “to” is used to indicate a physical or emotional movement towards something. In this case, it would not make sense to say that the listener is moving towards the Tans. The preposition “at” is used to indicate a location or position. In this case, it would not make sense to say that the listener is located at the Tans. The preposition “over” is used to indicate a position above or across something. In this case, it would not make sense to say that the listener is located above or across the Tans.