Which of the following represents an abiotic cause of plant problems?

The correct answer represents an abiotic cause of plant problems because abiotic factors refer to non-living physical and chemical elements in the environment that can affect plant health. Extreme drought conditions significantly hinder a plant's ability to obtain water, leading to stress, wilting, reduced growth, and even death. Such conditions can disrupt physiological functions and nutrient uptake, ultimately impacting the overall health and vitality of the plant.

In contrast, the other options involve biotic causes, which are associated with living organisms. Fungal infections, insect infestations, and bacterial leaf spots are all caused by biological agents that directly interact with the plant. These biotic factors can result in diseases or damage but do not pertain to non-living environmental conditions, which is why the extreme drought is the only correct choice as an abiotic factor.