What additional protection does PCNB provide?

PCNB, or pentachloronitrobenzene, is a fungicide widely used in seed treatment to provide protection against various fungal issues that can threaten seed health and development. It is particularly effective in managing seed rots, decays, and blights that can arise from soil-borne pathogens. This fungicidal action is crucial because such diseases can significantly hinder seed germination and ultimately reduce crop yields.

Selecting the option that states PCNB offers some protection against seed rots, decays, and blights underscores the role of this chemical in safeguarding seeds during their vulnerable early stages. This preventative measure is vital for ensuring that a greater number of seeds successfully germinate and grow into healthy plants.

The other options highlight different aspects that do not directly relate to what PCNB is designed to accomplish in seed treatment. While pests are a concern for seedling health, they are generally managed through different insecticides. Environmental risk mitigation is not a primary function of PCNB. Similarly, while shelf life can be important, the efficacy of PCNB is more focused on disease prevention rather than extending the intrinsic viability of the seeds themselves. Thus, the answer correctly emphasizes PCNB's role in disease protection.