Suppose Pitt Fitness offered personal fitness training and the Customers table were designed as follows:

Customers CustomerID, LastName, FirstName, StreetAddress, City, State, ZipCode, EmailAddress, PhoneNumber, BirthDate, InstructorID$)$

This design reflects that instructors also work as personal trainers. Which of the following fields is functionally dependent on InstructorID?

a$.$ LastName

b$.$ EmailAddress

c$.$ BirthDate

d$.$ None of the fields in the table is functionally dependent on InstructorID.