1-31The Finding That People with One Type of Serotonin Transporter

1-31.The finding that people with one type of serotonin transporter gene and childhood maltreatment had higher rates of depression than either those without the gene or those with the gene without the maltreatment suggests that

A) childhood maltreatment causes depression.
B) only one type of gene causes depression.
C) either or a gene or certain environmental factors need to be present to cause depression.
D) both a gene and certain environmental factors need to be present to cause depression.