The correct answer is: B. by-product.
A by-product is a secondary product of a manufacturing process that has relatively low value compared to the primary product. By-products are often used as raw materials for other products or are sold as a commodity.
Joint products are two or more products that are produced simultaneously from a single process. The value of joint products is often similar, but they can also have different values.
Seasonal products are products that are only available or in demand during certain times of the year. For example, Christmas trees are a seasonal product.
Economic products are products that have a positive economic value. This means that they are worth more than the cost of producing them.
In the case of the question, the low value product is called a by-product because it has relatively low value compared to the primary product.