The Discovery of the Drug Viagara Used Improved Sexual Performance

The discovery of the drug Viagara used improved sexual performance among males was a result of:

A) The accidental discovery of a side-effect of a drug being developed to treat coronary artery disease.
B) Years of research to address the problem of erectile dysfunction and improve the quality of life of men with the condition.
C) The discovery of a rare, naturally occurring herb found only in the rain forests in Central America, specifically Costa Rica and Belize.
D) An attempt by pharmaceutical companies to find a drug that they could market to otherwise healthy men.