How does molecular shape affect polarity? A. If the molecule is symmetric, the effects of polarity?

It's down to symmetry. With a symmetrical shape, the bond dipoles can cancel each other out. If something isn't symmetrical there will be some polarity.

If you Google the molecular structure of ammonia, for instance, you'll see that ammonia has eight electrons (five from the Nitrogen and one each from three Hydrogen atoms). Six of the electrons are pair-bonded (with the Hydrogen atoms) but two form a lone pair making ammonia unsymmetrical, making ammonia a proton acceptor, or base.