G9A07

What must be done to prevent standing waves on a feed line connected to an antenna?

1. AThe antenna feed point must be at DC ground potential
2. BThe feed line must be an odd number of electrical quarter wavelengths long
3. CThe feed line must be an even number of physical half wavelengths long
4. DThe antenna feed point impedance must be matched to the characteristic impedance of the feed line

Pick an answer to check it.