Of the two types of fungicides, which one is used to prevent plant diseases?

The selected answer is correct because protectants are specifically designed to form a barrier on the plant surface, preventing pathogens from establishing and causing disease. They are applied before a disease occurs, thereby actively preventing infections by inhibiting the development of fungi on plants. This preventive action is crucial in maintaining plant health, especially in scenarios where crops are exposed to conditions conducive to disease development.

In contrast, eradicants are intended to eliminate existing infections rather than prevent them. Systemic fungicides, while they can provide protective effects, primarily work by being absorbed into the plant and managing diseases that have already established. Fungistatics work by inhibiting the growth of fungi rather than preventing their occurrence outright. Therefore, protectants are the most appropriate choice for preventing plant diseases.