Which of the following elements is necessary for normal thyroid function?

A. The tricuspid valve has three leaflets and is located between the right atrium and right ventricle. It closes during ventricular contraction (systole) but does not have two leaflets.

B. The pulmonic valve has three leaflets and controls blood flow from the right ventricle to the pulmonary artery. It is closed during the systolic phase but is not the correct answer for having two leaflets.

C. The aortic valve has three leaflets and controls blood flow from the left ventricle into the aorta. It also closes during systole, but it does not have two leaflets.

D. The mitral valve, also known as the bicuspid valve, has two leaflets and is located between the left atrium and left ventricle. It closes during systole to prevent backflow of blood into the left atrium.

A. Luteinizing hormone (LH) is involved in the regulation of the menstrual cycle and ovulation, but it is not responsible for uterine contractions or milk production.
B. Lactogen (also known as human placental lactogen) is produced during pregnancy and helps prepare the breasts for milk production, but it does not trigger uterine contractions.
C. Oxytocin plays a key role in both uterine contractions during labor and milk ejection during breastfeeding. It is sometimes referred to as the "love hormone" because it is also involved in bonding and emotional connections.
D. Prolactin is responsible for stimulating milk production in the mammary glands, but it does not cause uterine contractions. Oxytocin is the hormone responsible for that function.