What Specific Physical Effect Was Used to Verify the Existence

Multiple Choice

What specific physical effect was used to verify the existence of intense magnetic fields in sunspots?

A) Observation of ionized atoms in the region of the sunspots
B) The Zeeman effect,the splitting of spectral absorption lines
C) The measurement of relative strengths of spectral absorption lines from various atoms
D) Doppler shift of light from sunspots