The scenario that would most likely reduce the number of inheritable traits in a population, thereby causing the individuals in that population to remain very similar to one another, is:
• A swamp that is being drained in order to build houses.
When a swamp is drained, it drastically alters the habitat and may lead to a significant reduction in the available environment for diverse species. This habitat loss can lead to a population bottleneck, where only a small number of individuals survive and reproduce. As a result, genetic diversity is reduced, leading to a more homogeneous population with fewer inheritable traits.
In contrast, the other scenarios (conversion of a forest to farmland, a long-established desert, and a drying lake) may not necessarily result in a similar level of genetic homogeneity or could potentially allow for some adaptation among surviving species, depending on their resilience and adaptability to changing conditions.