Answer: D.) He noticed that everything in the natural world had mathematical properties, and they could be used to study and measure everything.
Explanation: Kepler argued that God had created the world according to an intelligible plan that is accessible through mathematical means. Kepler was convinced "that the geometrical things have provided the Creator with the model for decorating the whole world". ( Caspar, Kepler, pp. 265–266, translated from Harmonices Mundi)