What hormone is responsible for the development of male secondary sexual characteristics?

Correct Answer: A

Rationale: Testosterone is the correct answer because it is the primary male sex hormone responsible for the development of male secondary sexual characteristics such as facial hair, deep voice, and muscle growth. Testosterone is produced by the testes in males. Progesterone (B) is a female sex hormone involved in the menstrual cycle and pregnancy. Estrogen (C) is the primary female sex hormone responsible for the development of female secondary sexual characteristics. FSH (D) is a hormone that stimulates the production of sperm in males and the maturation of eggs in females, but it is not directly responsible for male secondary sexual characteristics.

Correct Answer: B

Rationale: The correct answer is B: Stimulates uterine contractions. Oxytocin is a hormone released during childbirth that acts on the uterus to induce contractions, leading to the progression of labor. It plays a crucial role in facilitating the delivery of the baby. The other choices are incorrect because: A: Inhibiting uterine contractions would hinder the progress of labor. C: Oxytocin does not increase progesterone secretion; it primarily acts on the uterus. D: Oxytocin does not reduce fetal heart rate; instead, it helps in the expulsion of the baby by stimulating contractions.

Correct Answer: C

Rationale: The corpus luteum is formed from the ruptured follicle after ovulation. It secretes progesterone to prepare the uterine lining for implantation and maintain pregnancy. This is essential for supporting early pregnancy until the placenta takes over progesterone production. Choices A and D are incorrect as the corpus luteum primarily produces progesterone, not estrogen or stimulates follicle development. Choice B is incorrect as the corpus luteum does not prevent ovulation but rather supports pregnancy post-ovulation.

Correct Answer: B

Rationale: Testosterone is the correct answer because it is the primary male sex hormone responsible for the development and maintenance of the male reproductive system, including the development of male sex organs like the testes and penis. Estrogen (A) is the primary female sex hormone, not responsible for male reproductive system development. Progesterone (C) is involved in the female reproductive system and pregnancy, not in male development. FSH (D) is a follicle-stimulating hormone that plays a role in both male and female reproductive systems but is not responsible for the development of the male reproductive system specifically.

Correct Answer: B

Rationale: The primary purpose of the placenta during pregnancy is to provide oxygen and nutrients to the fetus. The placenta acts as a bridge between the mother and the fetus, allowing for the exchange of oxygen, nutrients, and waste products. It filters oxygen and nutrients from the mother's blood to the fetus and removes waste products from the fetal blood to the mother's circulation. This process ensures the proper growth and development of the fetus. Choice A is incorrect because the placenta does not excrete waste products, it filters them. Choice C is incorrect as the placenta does not regulate the fetus's temperature. Choice D is incorrect because hCG (human chorionic gonadotropin) is a hormone produced by the embryo, not the placenta.