Correct Answer: C

Rationale: An experimental design permits inferences about cause and effect because researchers evenhandedly assign people to treatment conditions. This means that researchers can manipulate certain variables and observe the effects on participants, allowing them to determine causation between variables. This is a key strength of experimental research designs. Choices A, B, and D are incorrect because they do not accurately describe the primary purpose or strength of experimental designs. Experimental designs do not focus on gathering information in natural life circumstances (A), looking at relationships between characteristics and behavior (B), or have the limitation of not being able to infer cause and effect (D).

Correct Answer: A

Rationale: Pregnant women are wise to avoid eating long-lived predatory fish, which are heavily contaminated with mercury. Mercury is a known teratogen, meaning it can negatively impact the development of the fetus and lead to birth defects. It is recommended that pregnant women choose fish with lower levels of mercury to reduce potential risks to the baby's health. Choices B, C, and D are incorrect because lead, polychlorinated biphenyls, and radiation are not typically found in fish at levels that pose significant risks to pregnant women and the developing fetus.

Correct Answer: B

Rationale: A major limitation of systematic observation is that it tells investigators little about the reasoning behind responses and behaviors. Systematic observation focuses more on recording observable behaviors rather than delving into the underlying reasons or thought processes driving those behaviors. Choices A, C, and D are incorrect because systematic observation can indeed provide detailed information on how participants actually behave, it doesn't necessarily underestimate the capacities of individuals who struggle with verbal expression, and it doesn't solely ignore participants with poor memories as it can capture behavior in real-time regardless of memory recall.

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: C

Rationale: Small-for-date infants more often show evidence of brain damage than preterm infants. This can be attributed to factors such as intrauterine growth restriction and poor nutrition during pregnancy, which can affect the development of the baby's brain. Choices A, B, and D are incorrect because there is no evidence to support that small-for-date infants catch fewer infections, are less likely to die, or have higher intelligence tests compared to preterm infants.