Correct Answer: B

Rationale: The correct answer is B because most metals are not gases at room temperature; they are usually solid and good conductors of heat. Metals are generally known for being good conductors of heat, ductile, and making up the majority of elements on the periodic table. Choice A is correct as metals, in general, are good conductors of heat. Choice C is also correct as most metals exhibit ductility. Choice D is correct as metals constitute the majority of elements found on the periodic table.

Correct Answer: C

Rationale: The alveoli are the tiny sac-shaped structures in the lungs where gas exchange occurs. Oxygen from the air we breathe diffuses into the bloodstream through the alveoli, while carbon dioxide, a waste product produced by cells, is removed from the blood and exhaled out of the body through the alveoli. Choices A, B, and D are incorrect. Kidneys are organs responsible for filtering waste from the blood, the medulla oblongata is a part of the brain responsible for autonomic functions, and bronchioles are smaller airway passages in the lungs that branch off from the bronchi.

Correct Answer: D

Rationale: The correct answer is D. The primary function of the endocrine system is to maintain homeostasis. Homeostasis refers to the stable internal conditions of the body, including body temperature, blood pH, and glucose levels. The endocrine system achieves this by releasing hormones that regulate various physiological processes and help keep the body's internal environment in balance. Choices A, B, and C are incorrect because while the endocrine system does influence heart rate, electrolyte and water balance, and respiration to some extent, its primary role is to regulate homeostasis by releasing hormones.

Correct Answer: C

Rationale: The circulatory system is responsible for transporting nutrients, gases, and wastes to and from the cells in the body. It includes the heart, blood vessels, and blood, which work together to distribute oxygen, nutrients, and remove waste products throughout the body. The respiratory system is primarily involved in gas exchange, the digestive system breaks down food for absorption, and the nervous system is responsible for transmitting signals throughout the body.

Correct Answer: C

Rationale: The correct answer is Covalent (C). In DNA, a covalent bond connects sugar and phosphate molecules. This bond involves the sharing of electron pairs between the atoms, providing stability to the DNA structure. Hydrogen bonds are important in DNA structure but are not the primary bond connecting sugar and phosphate. Ionic bonds involve the transfer of electrons, and 'overt' is not a term related to the bond connecting sugar and phosphate in DNA.