The correct answer is A. Only 1.
Decrease in demand is caused by change in factors other than own price of the commodity. This is because the demand curve is downward sloping, which means that as the price of a good decreases, consumers will demand more of it. However, if there are other factors that change, such as income, taste, or the prices of related goods, the demand curve can shift. For example, if income increases, consumers will demand more of all goods, including the good in question. This would cause the demand curve to shift to the right.
Contraction of demand is caused by decrease in own price of the same commodity. This is not correct. As explained above, a decrease in the price of a good will cause an increase in demand, not a decrease.
Extension of demand is caused by increase in own price of the same commodity. This is also not correct. As explained above, an increase in the price of a good will cause a decrease in demand, not an increase.