Common Descent Is Referred to as a Theory Because

Multiple Choice

Common descent is referred to as a theory because

A) there is overwhelming evidence to support it from many areas of biology.
B) scientists are reasonably sure it's true, but there's little evidence to support it.
C) it's an idea from more than 100 years ago and thus is not a modern idea.
D) it's the only idea about life on Earth that can be tested by observation of the material universe.