Question

a plant shows sudden wilting within hours after a cold night. this is most likely due to: viral infection herbicide drift frost injury fungal root rot

Explanation:

When a plant shows sudden wilting within hours after a cold night, frost injury is the most likely cause. Frost can damage plant cells, leading to rapid wilting. Viral infection and fungal root rot usually develop over a longer period, not suddenly after a cold night. Herbicide drift would also have a different set of symptoms and not be directly related to a cold night.

Answer:

C. Frost injury