The correct answer is: B. A luxury good
An essential good is a good that people need to survive, such as food, water, and shelter. The demand for essential goods is relatively inelastic, meaning that people will continue to buy them even if the price goes up.
A luxury good is a good that people do not need to survive, but that they enjoy having. The demand for luxury goods is relatively elastic, meaning that people will buy less of them if the price goes up.
An inferior good is a good that people consume less of as their income increases. The demand for inferior goods is negatively correlated with income.
A Giffen good is a good that people consume more of as their income increases, even though the price of the good is also increasing. Giffen goods are very rare, and they are usually only found in very specific circumstances.
In the case of good X, the income elasticity of demand is greater than zero but less than 1. This means that the demand for good X is positively correlated with income, but the relationship is not very strong. This suggests that good X is a luxury good.