Correct Answer: B

Rationale: Brain weight increases tenfold from the twentieth week until birth. This rapid growth and development of the brain during the prenatal period is crucial for setting the foundation for future cognitive and neurological functions. Choices A, C, and D are incorrect because although they also undergo changes during prenatal development, none of them increase tenfold from the twentieth week until birth, unlike brain weight.

Correct Answer: A

Rationale: Theorists who emphasize plasticity believe that change in response to influential experiences is possible. They argue that individuals have the capacity to adapt and change their behavior based on their experiences, rather than being limited by genetic predispositions or early childhood experiences. This perspective highlights the importance of environmental influences in shaping behavior and development. Choices B, C, and D are incorrect because they do not align with the concept of plasticity, which emphasizes the flexibility and adaptability of individuals in response to their experiences, rather than being fixed by heredity, childhood traits, or early experiences.

Correct Answer: C

Rationale: Rotunda, age 16, is the most likely to have had inadequate prenatal care due to her young age and possibly limited access to healthcare resources and support. Adolescents are at higher risk for inadequate prenatal care compared to older mothers due to various factors such as lack of awareness, financial constraints, and inconsistent health behaviors. Young mothers may face challenges in seeking proper prenatal care due to reasons like lack of knowledge, fear of judgment, or limited financial means. Older mothers like Lupe, Marissa, and Janette are less likely to have inadequate prenatal care compared to a younger mother like Rotunda, as they may have more access to resources, experience, and support systems.

Correct Answer: D

Rationale: Cross-sectional studies can be threatened by cohort effects because different age groups may have experienced different historical or social contexts, influencing the results. This disparity can lead to invalid comparisons between age groups, confounding the study's findings. Option A, practice effects, refer to changes in participants' behavior due to repeated testing, not a specific threat to cross-sectional studies. Participant dropout (Option B) is a threat related to attrition in longitudinal studies, not cross-sectional studies. Sequential timing (Option C) does not pose a threat to cross-sectional studies; instead, it refers to the order of tasks in a study design.

Correct Answer: C

Rationale: Three-month-old Jefferson will likely listen longer to human speech compared to nonspeech sounds because infants have a natural preference for speech sounds. This preference is believed to be attributed to their biological readiness to learn language and communicate with others. Choice A is incorrect because voices are a form of human speech, which is preferred over pure tones. Choice B is incorrect as noises do not necessarily engage infants' attention as effectively as human speech. Choice D is incorrect because Jefferson is more likely to listen longer to his native language rather than a foreign language at this early age.