Final answer:
Option (d), Archimedes is best known for making significant contributions to the fields of mathematics and engineering, like the principles of the lever and buoyancy, and advances in geometry.
Step-by-step explanation:
Archimedes was known for advancements in various fields, including mathematics and engineering. He is not directly associated with any of the choices given (determining that the Earth revolves around the Sun, calculating the Earth's true size, or determining that the Earth was round).
Instead, Archimedes was renowned for profound achievements such as articulating the principles of the lever and the buoyancy principle (Archimedes' Principle). He also contributed significantly to geometry, including the method for calculating the volume of a sphere and deriving an approximation to the value of pi.