Correct Answer: D

Rationale: The correct answer is the trachea. The trachea is the largest part of the airway and serves as the main passageway for air to enter and exit the lungs. It connects the larynx to the bronchi and is an essential component of the respiratory system. The alveoli, although crucial for gas exchange, are tiny air sacs in the lungs and not the largest part of the airway. Bronchi and bronchioles are smaller airway passages that branch off from the trachea, making them smaller in size compared to the trachea.

Correct Answer: A

Rationale: The correct answer is A: Neuron. Neurons are the fundamental building blocks of the nervous system. These specialized cells play a crucial role in transmitting information through electrical and chemical signals. While nerves are comprised of bundles of neurons and ganglia consist of clusters of nerve cell bodies located outside the central nervous system, neuroglia serve as support cells for neurons. Neurons are specifically responsible for processing and transmitting information within the nervous system, making them the essential unit of this complex system. Choices B, C, and D are incorrect as nerves are bundles of neurons, ganglia are clusters of nerve cell bodies outside the central nervous system, and neuroglia are support cells for neurons, not the fundamental units responsible for information processing and transmission.

Correct Answer: C

Rationale: Work is defined as the product of the force applied to an object and the distance over which the force is applied. In the situation of lifting a box to place it on a shelf, work is being done on the object. This is because lifting the box involves applying a force over a distance (the height of the shelf). The force applied to lift the box results in work being done on the object by raising it against the force of gravity. Choices A, B, and D do not involve work being done on the object as they either do not involve movement against a force (A, D) or do not cover distance against a force (B).

Correct Answer: C

Rationale: In most ecosystems, the primary source of energy is sunlight. This energy is captured by plants and other photosynthetic organisms through the process of photosynthesis. These organisms convert light energy into chemical energy stored in the bonds of organic molecules, such as glucose. This stored chemical energy is then passed on to other organisms in the ecosystem through the food chain, making sunlight the fundamental source of energy for most ecosystems. Thermal energy from the Earth's core (option B) is not a primary source of energy for ecosystems, as it is not readily accessible to most organisms. Kinetic energy from wind and water (option D) can play a role in some ecosystems, but it is not the primary source of energy. Chemical energy stored in bonds (option A) is a form of energy that is ultimately derived from the sun through photosynthesis, making it a product of the primary energy source rather than the primary source itself.

Correct Answer: A

Rationale: A) Desertification is the correct term for the gradual loss of topsoil due to wind or water erosion. It refers to the process by which fertile land becomes desert, usually due to factors like drought, deforestation, or inappropriate agriculture practices. This process can lead to the degradation of land and contribute to the expansion of deserts. B) Leaching is the process in which minerals are washed out of the soil by water moving downwards through it. This is different from the loss of topsoil due to erosion. C) Salinization occurs when salt accumulates in the soil, typically as a result of irrigation in arid regions. While salinization affects soil quality, it is not specifically related to the gradual loss of topsoil due to erosion. D) Acidification refers to the decrease in soil pH, often caused by factors like acid rain or the use of acidic fertilizers. This process is distinct from the gradual loss of topsoil due to erosion.