Diffusion is the random movement of particles from regions of higher concentration to lower concentration, and it doesn't require energy from the cell. Osmosis is a specific kind of diffusion: water moving across a selectively permeable membrane toward the side with higher solute concentration (lower water potential). The statement that ties these ideas together is the best because it defines diffusion in general and then identifies osmosis as diffusion of water through a membrane, making the relationship clear. Osmosis is water-specific, and it depends on the membrane being permeable to water but not necessarily to solutes, while diffusion applies to any substance moving down its own concentration gradient and can occur in gases, liquids, or solids. The other options misstate these points: diffusion is not energy-requiring, and it is not limited to liquids.

Increase in energy production comes from having more inner-membrane area to host the machinery that makes ATP. The folds of the inner mitochondrial membrane, called cristae, massively expand that surface area. With more membrane space, more electron transport chain complexes and ATP synthase units can be present, allowing more protons to be pumped and more ATP to be synthesized. The mitochondrial matrix is where the citric acid cycle occurs, not where the surface area for respiration is expanded. The outer membrane surrounds the organelle and doesn’t contribute directly to ATP production. Ribosomes are for protein synthesis and don’t increase the inner membrane’s surface area for energy generation.

Ecosystem services are the benefits humans receive from ecosystems. These include provisioning services like food, water, and medicines; regulating services such as climate regulation, flood control, and disease management; supporting services like pollination and nutrient cycling that keep ecosystems functioning; and cultural services including recreational, aesthetic, and spiritual value. This broader description best captures why ecosystems matter to people, beyond just the living organisms themselves. The other options describe a process (erosion rate), an abiotic factor (sunlight), or a biodiversity measure (number of species), none of which summarize the human benefits that ecosystems provide.

In a simple food chain, energy moves from producers that make their own food to primary consumers that eat those producers. When a predator eats herbivores, it’s one step higher up the chain, so it’s a secondary consumer. It isn’t a producer because it doesn’t synthesize its own food, and it isn’t a primary consumer because it doesn’t feed directly on producers. It would be a tertiary consumer only if it fed on other carnivores that have already eaten herbivores.

Diffusion is a passive process where particles spread from places of higher concentration to lower concentration because of their random motion, and it happens without the cell spending energy. In contrast, active transport moves substances against their concentration gradient—from low to high concentration—by using energy, usually from ATP, through specific pumps or transport proteins. This energy investment lets the cell concentrate essential substances inside even when they’re scarce outside. So the best description is that diffusion follows the concentration gradient without energy, while active transport uses energy to push substances up the gradient via pumps or transporters. The other statements confuse energy use or where diffusion can occur, so they don’t fit the idea of how these two processes differ.