Aristarchus measured the relative sizes of the earth, moon, and sun using eclipses and phase timings. since the moon is smaller than the earth and orbits the earth and the earth is smaller than the sun, he deduced that the earth must orbit the sun. this last phrase is what part of the scientific method?
a) observation.
b) theory.
c) prediction based on theory.
d) observation of prediction.
e) confirm/refute/modify theory.

This last phrase of the given sentence represents the theory part of the scientific method.

Option B

Explanation:

Aristarchus was a Greek scientist, who lived around 200 BC. He made an attempt to calculate the relative sizes of the earth and the moon, compared to the sun.His theory was based on the principle that, the distance (gap) between the sun and the earth, and that of earth and moon, is proportional to their diameters.And, he approximately calculated the angle as 87 degree, but is 89 actually. There, he did mistake, and he was even humiliated for this false theory, in his times.

An atom that has fewer electrons that protons is called a positive ion.

Does this your question?