The question is incomplete as there is no options given;
the complete question with options is;
Which column or columns in each table should be defined as the primary key?
a.Orders: OrderID; OrderLineItems: OrderID, OrderSequence, andProductID; Products: ProductID and ProductName
b.Orders: OrderID; OrderLineItems: OrderID and OrderSequence;Products: ProductID
c.Orders: OrderID and OrderDate; OrderLineItems: OrderID andOrderSequence; Products: ProductID
d.Orders: OrderID; OrderLineItems: OrderID; Products: ProductID
Answer:
the correct option from the given options is, "b",Orders: OrderID; OrderLineItems: OrderID and OrderSequence;Products: ProductID
when you are going to create a primary key, In Object Explorer, right-click the table to which you want to add a unique constraint, and then click Design. In Table Designer tab, click the row selector for the database column you want to define as the primary key.