Correct Answer: A

Rationale: The cell membrane, also known as the plasma membrane, serves as a protective barrier for the cell, separating the internal environment of the cell from the external environment. It is selectively permeable, meaning it controls the passage of substances in and out of the cell. This regulation of what enters and exits the cell is crucial for maintaining the cell's internal environment and ensuring proper functioning. Options B, C, and D are incorrect because storing energy, producing proteins, and synthesizing lipids are functions carried out by other cellular structures such as mitochondria, ribosomes, and endoplasmic reticulum, respectively, not the cell membrane.

Correct Answer: C

Rationale: The heart is located within the thoracic cavity, specifically in the mediastinum, which is the central compartment of the thoracic cavity. The thoracic cavity is part of the ventral cavity, which also includes the abdominal cavity. The dorsal cavity refers to the posterior side of the body and does not contain the heart. The heart is situated in the thoracic cavity between the lungs and above the diaphragm, making option C the correct choice.
Therefore, the correct answer is the thoracic cavity (option
C). The ventral cavity (option
B) includes the thoracic and abdominal cavities, but the heart is specifically situated in the thoracic cavity. The dorsal cavity (option
A) is located on the posterior side of the body, not where the heart is positioned. The abdominal cavity (option
D) is below the thoracic cavity and houses organs such as the stomach, liver, and intestines, but it does not contain the heart.

Correct Answer: A

Rationale: The correct answer is A: Melting. Melting is the process through which a solid substance changes directly into a liquid.
Choice B, Condensation, is the transition from gas to liquid.
Choice C, Sublimation, refers to the direct change from solid to gas.
Choice D, Deposition, is the direct transition from gas to solid, not from solid to liquid as in the question.

Correct Answer: B

Rationale: The small intestine is a crucial part of the digestive system responsible for absorbing nutrients into the bloodstream. This absorption primarily occurs through the villi lining the small intestine, which increases the surface area available for nutrient absorption. Nutrients like carbohydrates, proteins, fats, vitamins, and minerals are absorbed into the bloodstream to support various bodily functions such as energy production, growth, and repair.

Choices A, C, and D are incorrect as they do not accurately depict the primary function of the small intestine, which is nutrient absorption.

Correct Answer: C

Rationale: The correct answer is C, Gliding joint. Gliding joints allow for side-to-side bending movements. These joints are found between the small bones of the wrist and ankle, allowing for flexibility and movement in multiple directions. Hinge joints (
A) enable movement in one plane, akin to a door hinge. Ball-and-socket joints (
B) allow for a wide range of motion across multiple directions. Saddle joints (
D) facilitate movement in two planes.