Task: Class Definition Understanding (ontology: Sciences/Biology)

Which of the following definitions best describes 'primary amino compound'?

A. A compound formally derived from ammonia by replacing one hydrogen atom by an organyl group.
B. Any organic amino compound that contains two or more amino groups.
C. A primary amino compound that is phosphonic acid having a 1-aminoethyl group attached to the phosphorus.
D. A derivative of propylamine having a methylmercapto group at the 3-position.

Answer: A compound formally derived from ammonia by replacing one hydrogen atom by an organyl group.