What are sunspots?

• A. A bright region on the Sun's surface.
• B. A small asteroid group orbiting the Sun.
• C. A solar phenomenon caused by coronal mass ejections.
• D. Relatively cool, dark spots appearing periodically in groups on the Sun's surface, associated with strong magnetic fields.

Answer: (D)

Sunspots are relatively cool, dark regions that appear on the Sun’s visible surface. They form where intense magnetic fields suppress the normal heat transport from the Sun’s interior, so those patches stay cooler than the surrounding photosphere and look darker in contrast. They often occur in groups and rise and fall with the solar magnetic cycle, giving periods with many sunspots and periods with few.

This description fits because sunspots are cool, dark spots tied to strong magnetic activity and they appear in groups over time. The other options don’t match: they aren’t bright regions on the surface, they aren’t asteroid groups, and sunspots are not produced by coronal mass ejections (CMEs), which are eruptions in the outer solar atmosphere rather than surface features.