Correct Answer: B

Rationale: The correct answer is B. During prenatal development, the ectoderm folds over to form the neural tube, which eventually develops into the brain and spinal cord. The neural tube is the precursor to the central nervous system, including the primitive spinal cord. Choices A, C, and D are incorrect because the mesoderm does not form the neural tube, the endoderm is not involved in the formation of the central nervous system, and neuron tract is not the structure that forms the primitive spinal cord.

Correct Answer: A

Rationale: The correct answer is A, nurture. Nurture refers to the environmental influences that shape behavior and development. In this scenario, Justin's adoptive mother believes that providing sensitive caregiving will override the negative effects of his early experiences in the orphanage, highlighting the importance of nurture in promoting healthy development. Choice B, stages, is incorrect as it refers to the sequence of developmental milestones individuals pass through. Choice C, stability, is incorrect as it pertains to the consistency of behavior or development over time. Choice D, nature, is incorrect as it relates to genetic and biological factors influencing development, which is not the focus of Justin's mother's beliefs.

Correct Answer: D

Rationale: The difficulty in isolating the precise damage caused by illegal drugs during pregnancy is due to the fact that drug users often take several drugs, display other high-risk behaviors, and suffer from other stresses. This makes it challenging to identify the specific impact of each individual factor on prenatal development. Choices A, B, and C are incorrect because they do not address the complexity of the situation involving drug users during pregnancy. Most drug-using mothers refusing to participate in teratology research, the majority of babies not surviving, or drug-using mothers quitting during the first trimester do not directly explain the difficulty in isolating the precise damage caused by illegal drugs during pregnancy.

Correct Answer: D

Rationale: At around 4 months of age, babies begin to develop a preference for salty taste over plain water. This preference is part of their sensory development and exploration of tastes. Introducing a variety of flavors, including salty tastes, at this stage helps broaden the baby's palate and acceptance of different foods later on. Choices A, B, and C are incorrect as babies typically do not develop a preference for salty tastes over plain water at 2 weeks, 6 weeks, or 2 months of age. These earlier stages are more focused on milk feeding and the introduction of solid foods usually begins around 4-6 months of age.

Correct Answer: D

Rationale: The correct answer is D, the lifespan perspective. This perspective underscores the idea that individuals have the capacity for growth and change at any age, highlighting plasticity throughout the lifespan. It acknowledges the continuous development and adaptability of individuals to various experiences and factors. Choice A, the psychoanalytic perspective, focuses more on unconscious processes and early childhood experiences. Choice B, ethology, emphasizes the study of animal behavior in natural environments. Choice C, evolutionary developmental psychology, examines how evolutionary principles influence human development but does not specifically focus on plasticity at all ages.