Correct Answer: C

Rationale: The yolk sac is an extraembryonic membrane that plays a significant role in the early development of the embryo. One of its functions is to produce blood cells until the organs are mature enough to take over this function. This process occurs during the early stages of prenatal development to support the growing embryo before it can sustain itself independently.

Correct Answer: D

Rationale: Cigarette smoking by a caregiver doubles the risk of SIDS. Secondhand smoke exposure can increase the likelihood of SIDS due to the toxins and chemicals present in cigarette smoke. It is important to have a smoke-free environment for infants to reduce the risk of SIDS.

Correct Answer: A

Rationale: A 20-week-old fetus is able to be stimulated as well as irritated by sounds because by this stage of prenatal development, the fetus's auditory system is already well-developed. It can respond to external sounds and may even startle or move in reaction to loud noises.

Correct Answer: B

Rationale: Stress hormones during labor and delivery actually help arouse the infant into alertness. These hormones can promote the infant's readiness to adapt to the new environment outside the womb.

Correct Answer: B

Rationale: Babies who are both preterm and economically disadvantaged typically require long-term, intensive intervention. This is because the combination of being born preterm and being economically disadvantaged can pose significant challenges for the infant's development. Providing ongoing support and interventions can help address these challenges and promote healthy development in these infants.