The genetic influence on sexual orientation has been supported by research reporting that ____________ (a) between identical twins, if one brother is gay, the other brother has a 48 to 65 percent chance of also being gay; (b) gay men have fewer chromosomal pairs than straight men, whereas lesbians have larger areas of the hypothalamus than straight women; (c) between adoptive pairs of brothers, if the younger brother is gay, the older brother has an increased chance of also being gay.
(d) parenting style influences adult sexual orientation for men but not for women