According to the law of demand in microeconomics, how does the quantity demanded of a good change when its price increases, assuming other factors remain constant?

Introduction / Context:
The law of demand is one of the most fundamental ideas in microeconomics. It captures the typical behaviour of consumers in a market and explains why demand curves usually slope downward. Understanding this law is important for analysing how price changes affect consumer purchases, business decisions, and government policy outcomes. This question checks whether you can correctly state the core inverse relationship between price and quantity demanded when other factors are held constant.

Given Data / Assumptions:
- We are analysing the relationship between price and quantity demanded of a single good.
- All other determinants of demand, such as income, tastes, prices of related goods, and expectations, are assumed constant (the ceteris paribus condition).
- We consider a normal competitive market without extreme or exceptional behaviour.
- The question focuses on the direction of change rather than the exact numerical elasticity.

Concept / Approach:
The law of demand states that, other things remaining the same, there is an inverse relationship between the price of a good and the quantity demanded. As price rises, the quantity demanded tends to fall; as price falls, the quantity demanded tends to rise. This pattern is supported by the substitution effect, where buyers switch to cheaper alternatives, and the income effect, where a higher price reduces real purchasing power. The downward sloping demand curve in a price quantity graph is a visual representation of this law. Exceptions, such as Giffen goods, are rare and do not change the general rule tested in exams.

Step by Step Solution:
Step 1: Recall the standard wording of the law of demand: when price rises, quantity demanded falls, and when price falls, quantity demanded rises, other things equal. Step 2: Look for the option that clearly expresses an inverse relationship between price and quantity demanded. Step 3: Option A says that the higher the price, the lesser the quantity demanded, which exactly matches the law of demand. Step 4: Option B incorrectly claims that a higher price leads to a higher quantity demanded, which describes a direct relationship instead of an inverse one. Step 5: Option C suggests that higher quantity demanded causes higher price, confusing cause and effect and mixing demand with supply and market adjustment. Step 6: Option D cannot be correct because all three previous statements are not simultaneously consistent with the law of demand.

Verification / Alternative check:
Imagine a common product like tea. If the price of tea in the market doubles while people's incomes and preferences remain unchanged, most consumers will either reduce their consumption of tea or switch partly to other beverages. Quantity demanded falls because the relative cost of tea has risen. If the price falls sharply, people may buy more tea, or some who previously stopped buying return to the market. This everyday experience confirms that price and quantity demanded move in opposite directions, which supports option A.

Why Other Options Are Wrong:
Option B is wrong because it states a direct relationship between price and quantity demanded, which fits neither the law of demand nor the typical shape of a demand curve.
Option C is wrong because it describes a situation where quantity demanded causes price changes, confusing demand behaviour with market equilibrium adjustments.
Option D is wrong because only one of the statements correctly reflects the law of demand, so not all of them can be right at the same time.

Common Pitfalls:
Students sometimes mix up the law of demand and the law of supply and accidentally say that higher price leads to higher quantity demanded. Another common mistake is forgetting the ceteris paribus condition and thinking about other factors changing at the same time. It is also easy to confuse movement along a demand curve caused by a price change with a shift of the entire demand curve caused by changes in income or tastes. Keeping these distinctions clear helps to avoid errors in both theory and numerical problems.

Final Answer:
The higher the price of a good, the lesser the quantity demanded, other things being equal.