Answer:
b. perfectly inelastic.
Explanation:
A vertical demand curve means that quantity demanded would remain the same no matter the change in price. It means demand is perfectly inelastic.
Perfectly Inelastic demand means that quantity demanded doesn't respond to changes in price.
Demand is unit elastic if a small change in price has a greater effect on the quantity demanded.
Demand is perfectly elastic if quantity demanded falls to zero if there's a changes in price.
Demand is inelastic if a small change in price has little or no effect on quantity demanded.
I hope my answer helps you
