Final answer:
Sea ice melting has a warming effect on the atmosphere because less ice reflects the sun's rays, resulting in increased heat absorption by the ocean.
Step-by-step explanation:
The melting of sea ice has a warming effect on the atmosphere because there is less sea ice to reflect the sun's rays. Option b is correct. When sea ice melts, it exposes dark ocean water, which absorbs more solar radiation instead of reflecting it back into space. This leads to an increase in the amount of heat that is retained in the atmosphere, contributing to global warming.