The correct answer is: B. Increase in the price of the commodity concerned.
Contraction of demand is a decrease in the quantity demanded of a good or service at any given price. It can be caused by a number of factors, including:
- An increase in the price of the good or service.
- A decrease in the income of consumers.
- An increase in the prices of other goods or services.
- A decrease in the quality of the good or service.
- A change in consumer preferences.
In the case of an increase in the price of a good or service, consumers will tend to demand less of that good or service. This is because they have less money to spend on other goods and services, and they may also be able to find substitutes for the good or service that have not increased in price.
The other options are not correct because they do not directly affect the demand for a good or service. A decrease in the number of consumers will decrease the demand for a good or service, but this is not the same as an increase in the price of the good or service. An increase in the prices of other goods or services may lead to a decrease in the demand for a good or service, but this is only if the good or service is a substitute for the other goods or services. A decrease in the income of purchasers will decrease the demand for all goods and services, but this is not the same as an increase in the price of a specific good or service.
In conclusion, the correct answer is: B. Increase in the price of the commodity concerned.