Correct Answer: C

Rationale: Smooth muscle tissue is found in the walls of hollow organs such as the intestines, blood vessels, and bladder. It contracts involuntarily, allowing for functions like peristalsis in the intestines and regulation of blood flow in blood vessels. Skeletal muscle (Choice A) is attached to bones, cardiac muscle (Choice B) is found in the heart, and striated muscle (Choice D) refers to both skeletal and cardiac muscles due to their striped appearance, but neither of these types are typically found in the walls of hollow organs.

Correct Answer: A

Rationale: The main function of the digestive system is to break down food into nutrients through the process of digestion. Once the food is broken down, the nutrients are absorbed into the bloodstream and utilized by the body for various functions. Choice B, regulating body temperature, is incorrect as it is the function of the body's thermoregulatory system, not the digestive system. Choice C, transporting nutrients, is incorrect as the digestive system primarily focuses on breaking down and absorbing nutrients rather than transporting them. Choice D, producing hormones, is also incorrect as hormone production is mainly carried out by endocrine glands and not the digestive system.

Correct Answer: A

Rationale: The primary function of the respiratory system is to absorb oxygen from the air into the bloodstream and expel carbon dioxide from the body. This process is essential for cellular respiration and the production of energy in the body. Option A, 'To absorb oxygen,' aligns with this crucial function, making it the correct choice. Choices B, C, and D are incorrect as they do not represent the primary function of the respiratory system. The respiratory system is not responsible for transporting nutrients (choice B), producing sound and speech (choice C), or regulating blood pressure (choice D).

Correct Answer: A

Rationale: The correct answer is 'Epithelial.' Epithelial tissue is characterized by cells that cover internal and external surfaces, such as the lining of the stomach. It lacks an extracellular matrix, has tall and thin cells, and does not contain blood vessels. The other choices are incorrect because connective tissue typically has an extracellular matrix, muscle tissue is composed of contractile cells, and cartilage is a type of connective tissue with a specific extracellular matrix and cell arrangement.

Correct Answer: B

Rationale: White blood cells are a vital part of the immune system. Their primary function is to fight infections by attacking bacteria, viruses, and other pathogens that enter the body. They play a crucial role in protecting the body against illnesses and maintaining overall health. Choice A is incorrect because the role of carrying oxygen to cells is primarily performed by red blood cells. Choice C is incorrect as the transportation of nutrients is mainly carried out by the bloodstream and specialized cells. Choice D is incorrect as the process of clotting blood is primarily mediated by platelets.