The function being tested is the transport of gases in the blood. Erythrocytes, or red blood cells, carry oxygen from the lungs to tissues throughout the body using hemoglobin, which has heme groups that bind O2. This oxygen is released where it’s needed for cellular respiration. They also help remove carbon dioxide, a waste product of metabolism, by transporting it from tissues back to the lungs to be exhaled. CO2 is carried in several forms, including dissolved bicarbonate in plasma and as carbaminohemoglobin bound to hemoglobin, facilitating its removal. The efficiency of this gas exchange is aided by the red blood cells’ biconcave shape, which increases surface area for oxygen and carbon dioxide diffusion. Other options describe different blood components: protection against pathogens is the role of white blood cells and specific immune factors; preventing blood loss is primarily the job of platelets and clotting factors; and the listed item about water, proteins, electrolytes, nutrients, and hormones describes blood plasma composition, not the function of erythrocytes.

Amenorrhea is the absence of menstrual periods. This directly matches the definition, making the description of no menses the correct choice. The other terms describe different menstrual disturbances: heavy bleeding is menorrhagia, painful periods are dysmenorrhea, and irregular periods refer to an irregular or infrequent cycle (oligomenorrhea), not a complete absence. There are two main forms—primary and secondary amenorrhea—depending on whether menstruation has ever occurred or has stopped after it began.

Understanding breast anatomy means recognizing it as a mix of glandular and adipose tissue supported by connective tissue. The glandular part forms lobes with milk-producing lobules and ducts that drain toward the nipple, while fat tissue fills the surrounding space and varies with age and hormones. Ligaments provide structural support within the breast. Because of this combination, fatty tissue containing ducts, ligaments, lobes, and nipple best fits the structure of the breasts. The other options miss essential components: skeletal muscle and bone are part of the chest wall rather than the breast itself; dense connective tissue alone omits the glandular and fat components; cartilage is not a feature of breast tissue.

Major minerals are minerals required in amounts greater than 100 mg per day. These are also called macrominerals, and they include nutrients like calcium, phosphorus, potassium, sodium, chloride, magnesium, and sulfur. Because the body relies on them in larger quantities to support bone structure, fluid balance, nerve signaling, and muscle function, daily intake is relatively higher. The other ideas don’t fit: vitamins are not minerals, and fats stored in the body are lipids, not minerals. Minerals needed in smaller amounts fall into the category of trace minerals (less than 100 mg/day).