Martin and Halverson's gender schema model of gender-role development suggests that __
a. gender-roles don't begin to develop until a child reaches puberty and produces high levels of testosterone (boys) or estrogen (girls)
b. children are particularly interested in learning about objects or activities that fit their own-sex schemas.
c. children are passive participants in gender-role development.
d. children learn gender roles solely as a result of parental reinforcement of sex-appropriate behaviors and punishment of cross-sex behaviors.