In the very short period (market period), price is determined mainly by demand because:

1. The very short period (market period) refers to a period in which supply is fixed and cannot be increased or decreased. 2. With supply frozen, only demand can move, so price becomes demand-determined; a rise in demand raises price and vice versa. 3. Option B (all factors variable) is the long period, where supply fully adjusts to demand, so it cannot explain a demand-driven price. 4. Option C (free entry and exit) is a structural feature of perfect competition, not a property of the very short time period. 5. Option D (steadily falling costs) is unrelated to the time-element classification and is not stated as the cause. 6. Only the fixed-supply reasoning in A fits, so A is correct. _Source: ICAI BoS CA Foundation Paper 4 Business Economics, Ch 4 Unit I "Meaning and Types of Markets", p.3_