Why is it particularly useful to study identical twins who were raised in different environments?
a. it is possible that high concordance rates between identical twins reared together is due to their being treated more similarly than nonidentical twins.
b. concordance rates tend to be higher.
c. it is possible that the genetics of twins who have been separated have changed in ways to explain any differences found.
d. differences in brain function can easily be identified?

Based on the observation that only male crickets produce a song, you hypothesize that a male's song is a form of communication to potential mates. you set up a simple experiment to test this hypothesis. in the laboratory, you place a male snowy tree cricket in enclosure a, which is adjacent to enclosureb. in enclosure b, you place other insects, one at a time, and observe their responses to the male's song. the enclosures are designed so that the two insects being tested cannot see or smell each other, but sound is transmitted from enclosure a to enclosureb.