Who amongst the following was the first to state that the Earth was spherical?

Aristotle is the best answer. While the spherical idea was floated earlier by Pythagoreans (around 500 BC), Aristotle (384–322 BC) explicitly declared and defended the Earth’s sphericity on physical and observational grounds (e.g., lunar eclipses, changing star visibility, hull-first disappearance of ships), presenting this argument in On the Heavens around 350 BC [2]. The other choices postdate Aristotle: Ptolemy (geocentric mathematical model), Strabo (geographer), and Copernicus (16th-century heliocentrist) are later figures who either adopted or worked within later cosmological frameworks rather than being the earliest among these to state the Earth was spherical [1].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 2: The Solar System > Explanation: > p. 21
2. [2] https://www.astronomy.ohio-state.edu/thompson.1847/161/measearth.html