Concept:A demand curve shows the relationship between price and quantity demanded.
Necessity goods are usually bought in more or less the same quantity, but they still obey the law of demand.
Explanation:When the price of a necessity rises, the quantity demanded falls only slightly, not by a large amount.
This makes the demand for a necessity inelastic.
However, an inelastic demand curve is not vertical.
A vertical demand curve would mean quantity demanded never changes with price, which is not typical for a necessity.
A backward-bending curve is the shape of the labour supply curve, not a demand curve.
A horizontal curve means perfectly elastic demand, which is also not common for necessities.
Therefore, the usual demand curve for a necessity is steep but still slopes downwards from left to right.
This means it is negatively sloped.
Answer:D. negatively sloped