In an experiment, the group that serves as a point of reference for a comparison of results is the group

Dark adaptation takes about _____ minutes to complete; light adaptation is _____

(a) 30, quicker (b) 30, slower (c) 7, quicker (d) 7, slower

Across evolution, humans have competed most with ____ when trying to pass their genes passed down to subsequent generations

a. other opposite-sex humans b. other same-sex humans c. other animal species d. natural environmental forces