Why Did It Take Astronomers Until 1838 to Measure the Parallax

Multiple Choice

Why did it take astronomers until 1838 to measure the parallax of the stars?

A) because most stars are too faint to see without a good telescope
B) because the stars are so far away that their annual shift of position in the sky is too small to see without a good telescope
C) because detecting parallax requires measuring a spectrum, which only became possible in the 1830's
D) because cepheid variable stars had not been discovered earlier
E) because no one before then could conceive of the Earth moving around the Sun