Ad valorem duties are based on the

Ad valorem duties are import taxes that are calculated as a percentage of the value of the goods being imported. In other words, the amount of duty charged is based on the declared or assessed value of the imported goods. The higher the value of the goods, the higher the amount of duty charged. Ad valorem duties are commonly used by governments as a way to raise revenue and to protect domestic industries by making imported goods more expensive compared to locally produced goods. Therefore, "value of the goods imported" is the correct answer.