This prevents the water in the radiator from freezing when the temperature drops below 0°C, which is the freezing point of pure water.
(This; prevents; the water in the radiator; from freezing) (the temperature; drops; below 0°C) (0°C; is; the freezing point of pure water)
This the temperature 0°C
prevents drops is
the water in the radiator from freezing
below 0°C
the freezing point of pure water