Why is coaxial cable the most common feed line for amateur radio antenna systems?

Answer: A. It is easy to use and requires few special installation considerations

Coax is the most common feed line because it is easy to use and requires few special installation considerations. It can be run near metal and taped to towers without much trouble. It does not have the lowest loss of all feed lines, so that choice is wrong.

Tip: Coax wins on convenience.