A．We can't use different organisms as effectively as our ancestors did.
B．Biotechnology has done harm to the human being since prehistoric times.
C．Biotechnology can be used to modify human health and human environment.
D．Human therapeutic drugs are only dreams of human beings.

A．people have different responses to the question "what is biotechnology"
B．the question "what is biotechnology" has been posed to many people
C．responses to the question "what is biotechnology" should be made on the spot
D．only those who are asked the question "what is biotechnology" can answer it