$5\times3\times6=90$ 
A dinner set in a restaurant is free to choose a main course, a salad and a drink. Today, the restaurant offers five main courses, three salads, and six drinks for customers to choose. How many different sets can be matched? ． 
a. $14$ 
b. $30$ 
c. $48$ 
d. $80$ 
e. $90$ 