Review the following diagram. Which answer provides the best interpretation of the multiplicities for the association between the Product Categories and Supplier Categories classes?

a$.$ Supplier and product category information can be used to calculate year$-$to$-$date sales for each product$/$supplier category combination.

b$.$ Some employees may manage several product categories, and some employees may manage several supplier categories, but there is no direct link between supplier and product categories.

c$.$ Every supplier and product category can be managed by several employees, but no employee manages both.

d$.$ Each employee can only purchase products from one supplier category and for one product category.