The urine displaces a lot of nearby water as well. That surrounding water would initially be "clean" toilet water, but urine will mix into the water pretty quickly. That mixed water will then also displace as more urine hits the surface.
depends on the force of your stream and how close you are to the surface of the water
Probably a little column A, a little column B
It's both.
Here's a video of a water droplet, and you can see water (or urine) can actually bounce off the surface: https://www.youtube.com/watch?v=pbGz1njqhxU
And here's a simulated urine stream: https://www.youtube.com/watch?v=9c66KVU5ah8
The urine displaces a lot of nearby water as well. That surrounding water would initially be "clean" toilet water, but urine will mix into the water pretty quickly. That mixed water will then also displace as more urine hits the surface.
depends on the force of your stream and how close you are to the surface of the water