16. Philosophical problems arise when people ask questions that, though very _______ , have certain characteristics in common.

A) relevant B) elementary C) abstract D) diverse

17. Observable as a tendency of our culture is a _______ of belief in psychoanalysis: we no longer feel that it can solve our emotional problems.

A) defense B) withdrawal C) failure D) restoration

18. The advocates of recombinant DNA research have decided to _______ federal regulation of their work; they hope that by making this compromise they can prevent proposed state and local controls that might be even stiffer.

A) protest B) deny C) encourage D) disregard

19. Some scientists argue that carbon compounds play such a central role in life on Earth because of the possibility of _______ resulting from the carbon atom’s ability to form an unending series of different molecules.

A) deviation B) stability C) reproduction D) variety

20. Opponents of the expansion of the market economy, although in _______ , continued to constitute a powerful force throughout the century.

A) error B) retreat C) command D) effect