B. Weather.
Density-independent is usually something that affects the ecosystem no matter how much density, or how much population it has. Density-dependent is the opposite, the larger the density or population, the more damage it will cause. Disease, competition, and an abundant of food are all density-dependent things. If there is more population, disease will spread faster, competition begins with more density, and an abundant of food. Weather and climate changes, including natural disasters, are a prime example of a density-independent factor.
