Scenario B: When a large number of parasites are grown in a very small culture plate, they produce fewer eggs.

In population ecology, density-independent regulations refer to factors that influence population growth or decline regardless of the population density. These factors are typically abiotic or non-living factors that affect the population irrespective of its size. In the given scenarios, option B represents a density-independent regulation on population. Let's explore why:

1. Density-independent regulations:
Density-independent regulations are factors that affect the population growth rate regardless of the population size. These factors include natural disasters, climate events, and other abiotic factors. They often have a direct impact on the individuals in the population, leading to changes in birth rates, death rates, or reproductive success.

2. Scenario B explanation:
In scenario B, a large number of parasites are grown in a very small culture plate. This represents a controlled laboratory experiment where the population density of parasites is artificially increased in a confined space. The result is that the parasites produce fewer eggs.

The decrease in egg production can be attributed to various factors related to overcrowding in the small culture plate. These factors may include limited resources, increased competition for resources, accumulation of waste products, reduced space for movement and reproduction, and increased stress levels. These conditions can have a negative impact on the parasites' reproductive success, resulting in a decrease in egg production.

3. Differentiation from other options:
a) Option A: Squirrels population is limited due to less availability of nuts in a particular season.
This scenario represents a density-dependent regulation rather than a density-independent regulation. The availability of nuts in a particular season acts as a limiting factor that affects the population size based on resource availability. When nuts are scarce, squirrel populations may decrease due to decreased reproductive success and increased competition for resources.

c) Option C: The prevalence of diseases in a highly populated society.
This scenario represents a density-dependent regulation. In a highly populated society, the spread and prevalence of diseases can increase due to factors such as increased contact rates between individuals and reduced access to resources. The population density plays a critical role in disease transmission, making it a density-dependent factor.

d) Option D: A population of crows was limited when a hurricane destroyed their nests in the region.
This scenario represents a density-independent regulation. The hurricane, as a natural disaster, directly affects the population by causing the destruction of nests. This leads to a decline in the crow population, regardless of its size prior to the hurricane. Thus, it is a density-independent factor.

In conclusion, scenario B represents a density-independent regulation on population as it involves the impact of overcrowding on the reproductive success of parasites in a controlled laboratory experiment.