The sales typically measured by a manufacturer are

A) the quantity sold to final customers (sell-through) .
B) the quantity sold to distributors or retailers (sell-in) .
C) the quantity reported by the salesperson.
D) based on the quantity of supplies purchased from key suppliers.

The sales typically measured by a manufacturer are the quantity sold to distributors or retailers, also known as sell-in. This is because the manufacturer sells the products to the intermediaries who then sell them to the final customers. Sell-through, on the other hand, refers to the actual quantity purchased by the end customer, which may not be directly measurable by the manufacturer. The quantity reported by the salesperson may not always be accurate, and the quantity of supplies purchased from key suppliers may not directly reflect the manufacturer's sales.