The correct answer is: A. Less than unity.
The elasticity of demand is a measure of how responsive consumers are to changes in price. A good with an elasticity of demand less than unity is said to be inelastic, meaning that consumers are not very responsive to changes in price. This is often the case for durable goods, which are goods that are typically used for a long period of time and have a high purchase price. For example, if the price of a car goes up by 10%, consumers may not be very likely to stop buying cars, since they will still need a way to get around.
A good with an elasticity of demand greater than unity is said to be elastic, meaning that consumers are very responsive to changes in price. This is often the case for non-durable goods, which are goods that are typically used up quickly and have a low purchase price. For example, if the price of a candy bar goes up by 10%, consumers may be very likely to stop buying candy bars, since they can easily find other ways to satisfy their sweet tooth.
A good with an elasticity of demand equal to unity is said to be unitary elastic, meaning that consumers are neither very responsive nor very unresponsive to changes in price. This is relatively rare, but it can occur for some goods. For example, the demand for gasoline is often considered to be unitary elastic, since consumers are not very likely to stop driving if the price of gasoline goes up, but they are also not very likely to drive more if the price of gasoline goes down.
I hope this explanation is helpful!