Correct Answer: A

Rationale: The correct answer is A: 'any environmental agent that causes damage during the prenatal period.' A teratogen is any substance or factor that can cause harm to the developing fetus during pregnancy. Choice B is incorrect because it describes a critical period, not a teratogen. Choice C is incorrect as it refers to a specific period of development, not a teratogen. Choice D is incorrect because it describes a synthetic hormone, not a teratogen.

Correct Answer: D

Rationale: The correct answer is D. Development is best understood as a series of complex exchanges between nature (genetic factors) and nurture (environmental influences). This perspective emphasizes the interaction and interplay between genetic predispositions and environmental experiences in shaping an individual's development. Choices A and B are too extreme as they suggest that development is solely determined by genetics or solely influenced by the environment, which is not the case. Choice C is incorrect as development is not viewed as an unsolvable puzzle but rather as a dynamic process influenced by multiple factors.

Correct Answer: D

Rationale: Heaven is a preterm infant because she was born early, but her weight is appropriate for the time she spent in the womb. Choice A, 'small-for-date,' is incorrect as it does not specifically indicate that the infant was born before the due date. Choice B, 'small-for-weight,' is incorrect because the infant's weight is appropriate for the gestational age. Choice C, 'mature,' is incorrect as it does not reflect the early birth of the infant.

Correct Answer: C

Rationale: In females, the twenty-third pair of chromosomes is indeed labeled as XX. This pair of chromosomes determines the biological sex of females. Choice A, 'an autosome,' is incorrect as autosomes refer to the non-sex chromosomes. Choice B, 'dizygotic,' is incorrect as it relates to twins. Choice D, 'XY,' is incorrect as it represents the chromosome pair found in males.

Correct Answer: A

Rationale: Brain growth is especially dramatic during the first year of life when the brain more than doubles in size. This period is characterized by rapid neural development and growth. The brain doesn't double in size during the second year, making choice B incorrect. Middle childhood and adolescence do not represent periods where the brain more than doubles in size, making choices C and D incorrect, respectively.