Which column or columns in each table should be defined as the primary key?

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.