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: Albert Bandura's theory stresses the importance of cognition. Bandura's Social Learning Theory emphasizes the role of cognitive processes in learning and behavior, including the influence of observation, modeling, and mental representations. This theory highlights how individuals learn through observation and imitation of others, as well as their own thought processes and beliefs. Choices A, B, and D are incorrect because while behavior modification, punishment, and reinforcement are aspects related to learning theories, they are not the primary focus of Bandura's theory, which revolves around cognition and social learning.

Correct Answer: B

Rationale: Arnold Gesell is generally regarded as the founder of the child study movement, emphasizing the importance of observing and documenting children's behaviors to understand their development. While he was a significant figure in child development research, he did not specifically write child-rearing books for parents, foreshadow lifespan research, or construct the first successful intelligence test. Choice A is incorrect as Gesell's focus was more on research rather than writing child-rearing books. Choice C is incorrect as Gesell's main contributions were in child development, not specifically in aging research. Choice D is incorrect as Gesell is not credited with constructing the first successful intelligence test.

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: B

Rationale: One challenge associated with longitudinal research is that participants may relocate or drop out of the study over time. This can result in missing data and potential biases in the findings, impacting the study's overall validity and reliability. Furthermore, it can present difficulties for researchers in accurately monitoring and analyzing changes in individuals over an extended period. Options A, C, and D are incorrect because longitudinal research can indeed allow for inferences about cause-and-effect relationships, findings can be generalized to the real world with appropriate design and sampling, and it is suitable for studying individual developmental patterns.