Correct Answer: C

Rationale: The correct answer is C: Front portion of the parietal lobe. The motor cortex is located in the frontal lobe, specifically in the front portion of the parietal lobe. It is responsible for planning, controlling, and executing voluntary movements. Choices A, B, and D are incorrect as the motor cortex is not located at the back of the head, top middle portion of the parietal lobe, or around the auditory cortex.

Correct Answer: B

Rationale: The correct answer is the Hyoid bone. The hyoid bone is distinctive as it does not directly articulate with any other bone in the body. Instead, it is held in place by muscles and ligaments, playing a crucial role in supporting the tongue and providing attachment points for various muscles involved in swallowing and speech. The other choices, Femur, Radius, and Tibia, all articulate with other bones in the body. The femur articulates with the hip bone, the radius articulates with the ulna and other bones in the wrist, and the tibia articulates with the femur and fibula.

Correct Answer: A

Rationale: The spleen plays a crucial role in the immune system by filtering blood, specifically removing old or damaged red blood cells. It also stores lymphocytes, which are white blood cells that help fight infections. While the spleen does not produce white blood cells or antibodies, its main functions lie in blood filtration and storage of immune cells. Therefore, the correct answer is A. Choice B is incorrect because the spleen does not produce white blood cells. Choice C is incorrect as the spleen stores lymphocytes but does not primarily function to do so. Choice D is incorrect because the spleen does not produce antibodies.

Correct Answer: B

Rationale: The correct answer is B: 'They secrete chemicals into the blood.' Endocrine glands release hormones directly into the bloodstream to regulate various body functions. This process helps in maintaining homeostasis and coordinating different physiological processes within the body. Choice A is incorrect as endocrine glands do not absorb chemicals from the blood; instead, they release hormones. Choice C is incorrect as endocrine glands do not filter chemicals from the blood; they secrete hormones. Choice D is incorrect as endocrine glands do not absorb chemicals from the lymphatic system; they release hormones into the bloodstream.

Correct Answer: D

Rationale: The larynx is a vital organ of the respiratory system, responsible for producing sound and connecting the pharynx to the trachea. It plays a crucial role in breathing, swallowing, and vocalization. The brain, pancreas, and urethra are not part of the respiratory system; the brain is part of the nervous system, the pancreas is part of the digestive system, and the urethra is part of the urinary system. Therefore, the correct answer is the larynx.