In the sentence "In truth, Verne was neither a scientist nor an engineer: he was simply a writer and a very prolific one. ", the word "prolific" probably means ______.

A．A stranger.
B．A scientist whose job was to discover the future and cast new technology in a darker light.
C．From the start, the father of science fiction was gravely concerned with the dangers of technology.
D．He was either a scientist or an engineer.