Correct Answer: D

Rationale: Sydney's approach of starting with a hypothesis, deducing testable inferences, and isolating and combining variables to confirm inferences aligns with the characteristics of the formal operational stage in Piaget's theory of cognitive development. This stage typically emerges during adolescence and is characterized by advanced logical thinking, abstract reasoning, and the ability to think systematically about all possible outcomes of a problem. Choice A, sensorimotor, is incorrect as it pertains to the stage where infants learn through sensory experiences and motor actions. Choice B, preoperational, is incorrect as it involves egocentrism and lack of conservation. Choice C, concrete operational, is incorrect as it focuses on operational thought and logical reasoning in concrete contexts.

Correct Answer: C

Rationale: Dr. Singh's beliefs align with Erik Erikson's psychosocial theory of development. Erikson proposed that individuals go through a series of psychosocial stages, with each stage characterized by a basic conflict that must be resolved to achieve healthy development. This conflict is resolved along a continuum from positive to negative outcomes. Choice A, G. Stanley Hall, is incorrect as his work focused on adolescence and evolutionary psychology. Choice B, Sigmund Freud, is incorrect as his psychoanalytic theory is more focused on the unconscious mind and psychosexual stages. Choice D, B. F. Skinner, is incorrect as he is associated with behaviorism and operant conditioning, which is different from Erikson's psychosocial theory.

Correct Answer: C

Rationale: The statement that is true about a blastocyst is that between the seventh and ninth days, it burrows deep into the uterine lining. This process, known as implantation, is essential for the blastocyst to establish a connection with the mother's body and receive nutrients for further development. It is a critical stage in prenatal development and sets the foundation for pregnancy. Choices A, B, and D are incorrect. A blastocyst is not a single cell but rather a structure composed of many cells. It is not a structure that feeds the developing organism; instead, it implants in the uterine lining to receive nutrients. It is not a membrane that regulates temperature but plays a crucial role in the initial stages of pregnancy by implanting in the uterus.

Correct Answer: C

Rationale: To avoid exposure to toxoplasmosis, Kaye should ask other family members to change the litter box. Toxoplasmosis is a parasitic infection that can be transmitted through cat feces, so it is important for pregnant women to avoid handling cat litter to reduce the risk of infection. Choices A, B, and D are incorrect because they are not directly related to preventing toxoplasmosis. Smoking cessation is important for overall health but not specifically to prevent toxoplasmosis. Picking up after the dog and feeding the fish are not relevant to preventing toxoplasmosis, as the infection is primarily associated with cat feces.

Correct Answer: D

Rationale: In ecological systems theory, the chronosystem refers to the dimension of time and how events and transitions over time can influence an individual's development. Toby's move just before entering fourth grade represents a significant change in his life that falls under the chronosystem. The microsystem involves the immediate environments and relationships that directly influence an individual, the mesosystem relates to connections between these environments, and the exosystem includes external settings that indirectly influence the individual, such as parents' workplaces. Therefore, Toby's move best exemplifies a change in the chronosystem due to the temporal influence on his development.