Correct Answer: A

Rationale: Epithelial tissue is the correct answer as it aligns with the description provided in the question. Epithelial tissue is characterized by tightly packed cells with minimal extracellular matrix, which allows it to form protective barriers on the body's surface and line internal organs, providing structural support and protection. Connective tissue, while important for support and connection between tissues and organs, does not fit the description in the question of being tightly packed with minimal extracellular matrix. Muscle tissue is responsible for movement, and nervous tissue transmits signals throughout the body, neither of which are primarily involved in providing structural support and protection as described.
Therefore, based on the characteristics described in the question, epithelial tissue best fits the description of tissue that provides structural support and protection.

Correct Answer: B

Rationale: The correct answer is B. The two main types of nuclear decay are alpha and beta decay, which are differentiated based on the emitted particle. In alpha decay, an alpha particle (consisting of two protons and two neutrons) is emitted from the nucleus, while in beta decay, a beta particle (either an electron or a positron) is emitted. These decay types are distinguished by the particles they emit, not by the size of the nucleus, trigger, or stability of the nucleus.

Choices A, C, and D are incorrect because fission, fusion, spontaneous, induced, isotope decay, and chain reactions are different processes in nuclear physics and do not represent the two main types of nuclear decay based on emitted particles.

Correct Answer: D

Rationale: The correct answer is D: Mouth. The mouth is the organ that helps break down food by grinding it with your teeth. The process of chewing, also known as mastication, breaks down food into smaller pieces, making it easier to swallow and digest. The teeth in the mouth play a crucial role in this initial stage of digestion by physically breaking down food into smaller particles. The other options listed, such as the stomach, esophagus, and liver, do not directly participate in the mechanical breakdown of food through chewing. The stomach is responsible for further digestion through chemical processes, the esophagus is a muscular tube that helps transport food to the stomach, and the liver is primarily involved in metabolic functions and bile production.

Correct Answer: A

Rationale:
Rationale:

A)
To protect the body from harm: The skin acts as a physical barrier that protects the body from external threats such as pathogens, UV radiation, and physical injuries. It helps prevent infections and dehydration, making it a crucial function of the skin.


B)
To regulate body temperature: While the skin does play a role in regulating body temperature through processes like sweating and vasodilation/vasoconstriction, its primary function is protection.


C)
To produce hormones: Hormone production is primarily carried out by endocrine glands such as the pituitary gland, thyroid gland, and adrenal glands, not the skin.


D)
To sense touch, temperature, and pain: The skin contains sensory receptors that allow us to perceive touch, temperature, and pain, but this function is secondary to its main role of protecting the body from harm.

Correct Answer: D

Rationale: Work is defined as the product of the force applied on an object and the displacement of the object in the direction of the force. This means that work is only done when the force and displacement are in the same direction. If the force and displacement are not in the same direction, only the component of the force in the direction of the displacement contributes to the work done.
Therefore, choice D correctly defines work in terms of force and displacement.

Choices A, B, and C are incorrect because work is specifically calculated based on the force and displacement in the direction of the force, not in any direction, only when the displacement is vertical, or when the force and displacement are perpendicular.