Parallaxes of stars were not observed by ancient astronomers. how can this fact be reconciled with the heliocentric hypothesis?

May someone explain how to do this question?

Let v1, v2, w be three linearly independent vectors in r 3 . that is, they do not all lie on the same plane. for each of the following (infinite) set of vectors, carefully sketch it in r 3 , and determine whether or not it is a vector space (i.e., a subspace of r 3 ). explain your reasoning

How to tell if a molecule is polar or nonpolar with electronegativity