According to the article Chip Off the Old Block which discussed genetics and the Colorado Adoption Project, the groups of twins which were the primary groups in the Minnesota study which was discussed in the introduction were:

Which of the following statements regarding lethal genes is TRUE?

a. On average, people carry 6-8 lethal genes. b. Lethal genes are usually dominant genes. c. Only a very few lethal genetic disorders are caused by recessive lethal genes. d. Dominant lethal genes most often express themselves in spontaneous abortions and stillborn babies. e. Recessive lethal genes are only expressed when paired with a dominant lethal gene.

A 90-year-old woman kills herself rather than continue suffering with terminal bone cancer. A teenager commits suicide when his girlfriend breaks up with him and his parents are unconcerned. A religious fanatic kills himself to protest religious persecution. These examples of suicide suggest that ____

a. suicide cannot be studied in a scientific manner b. all suicide stems from mental disorder c. there are many different reasons for suicide d. suicide is basically a sociological phenomenon