Which of the following factors is the main problem facing xerophytic plants?

Analyze the question: It asks for the main problem faced by xerophytes. The word "xerophyte" is the key.

Explain the concept: Xerophytes are plants adapted to live in dry (arid) habitats such as deserts and semi-arid areas. The Greek root xero means "dry". Examples include cactus, agave, and some acacia species.

Solution, step by step:

• A. Competition for sunlight: This is a problem for plants in dense forests, not in open, sparse desert areas where sunlight is plentiful. Wrong.
• B. Conservation of excess water: Xerophytes conserve water, but they have no excess water. Conservation is their adaptation (thick cuticle, reduced leaves, sunken stomata, water-storing stems), not their problem. Wrong.
• C. Inadequate roots for water absorption: Xerophytes usually have well-developed roots, either deep tap roots or widespread shallow roots, so roots are not the problem. Wrong.
• D. Lack of adequate water: Dry habitats have little rainfall and high evaporation, so water scarcity is the central challenge. All of the xerophyte's adaptations exist to deal with this. Correct.

Answer: D. Lack of adequate water.

Tip: In WASSCE and JAMB questions, separate the problem (water scarcity) from the adaptations (reduced leaves, thick waxy cuticle, sunken stomata, deep roots, succulent stems). If an option describes a solution rather than a problem, it is usually a distractor.