What defines hygroscopic nuclei?

Hygroscopic nuclei are essential components in the atmospheric process that leads to cloud formation. These are microscopic particles, such as dust, salt, or smoke, that attract water vapor from the atmosphere. When water vapor condenses onto these hygroscopic nuclei, it forms tiny water droplets, which can aggregate to create clouds.

The correct answer emphasizes the role of these particles in aiding the formation of clouds, underscoring their significance in meteorological processes. Without hygroscopic nuclei, the condensation process that leads to cloud formation would be far less efficient, as pure water vapor typically requires a surface to condense on, which is provided by these particles. Therefore, the definition provided in the correct answer encompasses the fundamental role that hygroscopic nuclei play in the formation of clouds, making it the right choice.