Question

why might hakou be generally warmer than harbin? it is farther south & closer to the equator it is higher elevation it is farther north & far away from the equator

Explanation:

Areas closer to the equator receive more direct sunlight, leading to warmer average temperatures. Haikou is located in southern China, much closer to the equator than Harbin, which is in northern China. Higher elevation would cause cooler temperatures, and being farther from the equator would also lead to cooler conditions.

Answer:

A. It is farther South & closer to the equator