Final answer:
Rainwater from Luton ends up in the River Thames through surface runoff and groundwater seepage.
Step-by-step explanation:
Rain that falls on Luton ends up in the River Thames due to the natural process of surface runoff and groundwater seepage. When it rains, the water can either run off the surface directly into the river or seep into the ground and eventually make its way to the river. The River Thames is part of the drainage basin or watershed of the area, which means that all the water from the surrounding land flows into it. This includes rainwater from Luton.