Correct Answer: A

Rationale: A fetal heart rate of 60 beats per minute is significantly below the normal range (110-160 bpm) and indicates fetal distress, requiring immediate intervention. This low heart rate can be a sign of fetal compromise or distress, necessitating urgent evaluation and intervention to ensure the well-being of the fetus. Choices B, C, and D do not indicate immediate fetal distress requiring urgent intervention. Ruptured amniotic membrane, onset of uterine contractions, and leaking amniotic fluid are important assessments but do not present an immediate threat to the fetus's life like a severely low fetal heart rate.

Correct Answer: C

Rationale: Teratogens are environmental agents, such as drugs, chemicals, or infections, that can cause harm to a developing embryo or fetus. Mutations (Choice A) refer to changes in the DNA sequence and are not environmental agents. Autosomes (Choice B) are chromosomes that are not involved in determining an individual's sex and are not environmental agents that harm the embryo or fetus. Androgens (Choice D) are a group of hormones that are more related to male sexual development and function, not environmental agents that harm the embryo or fetus.

Correct Answer: B

Rationale: Folic acid deficiency during pregnancy is strongly associated with neural tube defects like spina bifida occulta. Adequate folic acid intake before and during early pregnancy significantly reduces the risk of such complications. Tobacco use (Choice A) is linked to other adverse outcomes but not specifically spina bifida occulta. Short intervals between pregnancies (Choice C) can increase the risk of preterm birth and low birth weight but are not directly linked to spina bifida occulta. Preeclampsia (Choice D) is a hypertensive disorder that poses risks to both the mother and baby but is not the primary factor contributing to spina bifida occulta development.

Correct Answer: C

Rationale: The correct answer is C: uterus. The uterus is the organ where the embryo implants and the fetus develops during pregnancy. The placenta (choice A) is an organ that develops during pregnancy and provides nutrients and oxygen to the fetus, but it is not the organ where the embryo and fetus physically develop. The ovum (choice B) is the female reproductive cell or egg that is fertilized by the sperm to form an embryo, but it is not the organ where the embryo and fetus develop. The amniotic sac (choice D) is a membrane filled with amniotic fluid that surrounds and protects the fetus, but it is not the organ where the embryo and fetus physically develop.

Correct Answer: B

Rationale: The correct answer is B: double helix. DNA is structured as a double helix, resembling a twisted ladder made up of two strands of nucleotides. Choice A, single spiral, is incorrect as DNA is not a single spiral structure. Choice C, sphere, is incorrect as DNA does not form a spherical shape. Choice D, cube, is incorrect as DNA does not have a cubic structure. Understanding the double helix structure of DNA is essential as it allows for the storage and transmission of genetic information in living organisms.