The correct response is:
Heat will flow from the iron block to the water until both reach a temperature somewhere between 50 degrees Celsius and 25 degrees Celsius.
This is because the iron block is at a higher temperature (250 degrees Celsius) compared to the water (50 degrees Celsius), so heat will transfer from the hot iron block to the cooler water until the two reach thermal equilibrium, which will be a temperature that is between the initial temperatures of the two substances.