If Someone Says That an Idea Is "Only a Theory

If someone says that an idea is "only a theory" and implies that this means it can be dismissed, is this a valid viewpoint?

A) The viewpoint is accurate because since science is based on interpretation it is not really trustworthy.
B) The viewpoint is accurate because a theory is essentially just a guess.
C) The viewpoint is incorrect because for an idea to become a theory it has withstood robust testing and is currently accepted.
D) The viewpoint is incorrect because once an idea becomes a theory it can never be disproven.