What is one major difference between a sales tax and a Value$-$Added Tax $($VAT$)?$

a$.$ VAT is collected at each stage of production, while sales tax is applied only at the final retail sale.

b$.$ Sales taxes are collected at multiple stages of production, whereas VAT is collected only at the point of sale.

c$.$ VAT is considered more regressive than sales taxes.

d$.$ Sales taxes are used only in the United States, while VAT is a global standard.