The correct arrangement of food classes of the same quantity in the order of magnitude of energy value in animals in descending order is

Analyze the question: We are asked to rank food classes (equal quantities) by energy value, from highest to lowest.

Concept: Energy values per gram:

• Fats and oils: about 37–39 kJ/g (9 kcal/g)
• Carbohydrates: about 17 kJ/g (4 kcal/g)
• Proteins: about 17 kJ/g (4 kcal/g)
• Water: 0 kJ/g (no energy)

Fats and oils give more than twice the energy of the others. Carbohydrates and proteins are almost equal, but in the standard textbook ranking used for WASSCE, carbohydrates (about 17 kJ/g) are placed slightly ahead of proteins (about 16–17 kJ/g). Water gives no energy at all, so it comes last.

Step-by-step solution:

1. Highest: fats and oils
2. Next: carbohydrates
3. Next: proteins
4. Lowest: water

This gives: Fats and oils > Carbohydrates > Protein > Water

Check the options:

• A. Carbohydrates placed above fats, and water placed above protein. Wrong.
• B. Fats and oils, carbohydrates, protein, water. This matches our ranking.
• C. Water placed first. Wrong, since water has no energy value.
• D. Protein placed first. Wrong.

Tip: Remember "F-C-P-W" (Fats, Carbs, Proteins, Water) as "Fast Cars Puncture Wheels". Also remember that water, minerals, and vitamins do not supply energy, so they always come last in energy-value questions.