The velocity of any object moving in a circular orbit is calculated by dividing the total distance covered by the time taken to cover that distance. For Earth moving around the sun, the total distance covered in a year is approximately the circumference of Earth`s orbit (which approximates to a circle) around the sun. The average distance from the earth to the Sun is about 150 million kilometers or 1 Astronomical Unit. Thus, the total distance of Earth`s orbit is around 2π times 150 million kilometers or about 940 million kilometers. Dividing this by the time it takes the Earth to orbit the Sun (about 365.25 days or 31.6 million seconds) gives an average velocity of about 30 kilometers per second (km/s). This is why option 2 (30 km/s) is the correct answer. The other options are incorrect because the values they give either underestimate or overestimate the true mean velocity of Earth`s orbit around the Sun.