Which is correct? Ptolemy model of the universe had circles upon circles a. to explain why Venus goes through phases as seen from Earth

b. to explain the fact that planets sometimes appear to move westward, rather than eastward, relative to the stars in our sky

c. to explain why more distant planets take longer to make a circuit through the constellations of the zodiac

d. to explain why the Greeks were unable to detect stellar parallax

e. to properly account for the varying distances of the planets from Earth