In the mismeasure of women, the social psychologist carol tavris argues that there is nothing "universal and nonvarying . . in the natures of men and women." if you agree with her, you would have to reject:

Human sexual dimorphism

Explanation:

Sexual dimorphism is a characteristic of certain species where the two sexes exhibit different characteristics that go beyond the differences in their sexual organs. The differences might include size, weight, colour, markings, behavioral and cognitive differences. In this passage, Carol Tavris argues that the natures of men and women are not different in any "universal" way. This seems to reject the idea of human sexual dimorphism.

answer; rational if melanie values sleep more highly than the benefits she expects to receive from attending the class;