The state of tension created by biological needs is called a(n) __________

Michelle and Deana are arguing about the relative benefits of breastfeeding and bottle feeding. Which of their arguments is most valid?

a. Michelle's claim that breastfed babies are ill less often because breast milk has the mother's antibodies in it. b. Deana's assertion that bottlefed babies are less likely to have diarrhea and constipation. c. Michelle's argument that breastfed babies' psychological development is enhanced. d. Deana's belief that bottlefed babies make the transition to solid foods more easily.

The two research methods scientists use to measure whether and how children change over time are

A) correlational and experimental research. B) correlational and observational research. C) cross-sectional and experimental research. D) cross-sectional and longitudinal research.