Final answer:
Cardano played a significant role in defining and developing complex numbers, which opened up new possibilities in mathematics and physics. Option D
Step-by-step explanation:
The mathematician who played a significant role in defining and developing complex numbers was Cardano.
His motivations were to understand and solve polynomial equations, and to find a way to calculate the square root of negative numbers. Cardano introduced complex numbers as a way to represent the roots of cubic equations, even though he did not fully understand their properties at the time.
Cardano's findings in complex numbers laid the foundation for further developments in mathematics and physics, and they opened up new possibilities in solving equations and understanding the complex plane. Option D