Q21

Robin Tang is a recruitment agent.As a client is placed with an employer, the employment table records this relationship.

Robin surveys employers and clients about the employment experience.

Results from the survey are stored in the Survey table.In the Client table, clients are uniquely identified by social security number.

What would the primary key be in the Employment table?

1.Social Security Number

2.Employer Number

3.Start Date

4.Social Security Number, Employer Number