Final answer:
An observer would never see Polaris at the Equator or the Tropic of Cancer, but would always see it at the North Pole. At the South Pole, Polaris is never visible.
Step-by-step explanation:
An observer would never see Polaris in the nighttime sky at the Equator (A). At this location, Polaris is on the horizon and not easy to see. As you move further south, such as at the Tropic of Cancer (C), Polaris is no longer visible. However, at the North Pole (B), Polaris is directly overhead, at the zenith, and is always visible in the nighttime sky. Similarly, at the South Pole (D), Polaris is never visible, but the southern half of the sky can be seen.