Correct Answer: B

Rationale: Ethical standards permit deception in research studies if investigators satisfy institutional review boards that such practices are necessary. Institutional review boards are responsible for ensuring that research studies comply with ethical guidelines and protect the welfare of study participants. Deception should only be used when necessary, and the board's approval indicates that safeguards are in place to minimize harm to participants. Choices A, C, and D are incorrect because ethical deception in research studies is not based on the age of participants, observing from behind mirrors, or obtaining informed consent without revealing the study's real purpose.

Correct Answer: B

Rationale: The correct answer is B. The corpus luteum is a temporary endocrine structure in the ovary that forms after ovulation. It secretes hormones, particularly progesterone, which help prepare the uterine lining for possible implantation of a fertilized ovum. This process is crucial for maintaining a potential pregnancy. Choices A, C, and D are incorrect. Choice A is inaccurate as fertilization typically occurs in the fallopian tubes. Choice C describes the fallopian tubes, not the corpus luteum. Choice D refers to the ovaries, not specifically the corpus luteum.

Correct Answer: B

Rationale: By using random assignment of participants to treatment conditions, investigators increase the chances that participants' characteristics will be equally distributed across treatment groups. Random assignment helps reduce the likelihood of bias in the selection process and ensures that any differences between groups are due to the treatment and not pre-existing group differences. Sequential, systematic, and correlational assignment methods do not provide the same level of assurance in distributing participants' characteristics equally across treatment groups.

Correct Answer: A

Rationale: Anesthetics, such as epidurals, are a strong type of painkiller used in labor and delivery that block sensation. They work by numbing the nerves in the lower part of the spine, providing pain relief during childbirth. Choice B, Analgesics, are pain relievers that reduce pain without causing loss of consciousness, but they are not as strong as anesthetics for labor pain. Choice C, Anti-inflammatories, are medications that reduce inflammation and do not directly block sensation like anesthetics. Choice D, Folic acids, are a type of B vitamin crucial for cell growth and metabolism, not used as painkillers in labor and delivery.

Correct Answer: B

Rationale: During the first week of pregnancy, the zygote (fertilized egg) undergoes rapid cell divisions and forms a blastocyst. This is a crucial stage where the cells differentiate and specialize, setting the foundation for the development of the embryo. It is during this time that the zygote implants itself into the uterine wall, initiating the process of pregnancy. Choices A, C, and D are incorrect because during the first week of pregnancy, the focus is on the initial development and multiplication of the zygote, not on the development of heart muscles, a primitive brain and spinal cord, or the embryo's ability to move.