It was a fabulous idea.

The correct answer is A. excellent.

A fabulous idea is one that is very good or outstanding. It is an idea that is likely to be successful and to have a positive impact.

B. fruitful is an idea that is likely to produce good results. C. legendary is an idea that is famous or well-known. D. precious is an idea that is valuable or important.

All of these words have positive connotations, but only excellent describes an idea that is both good and likely to be successful.