Which of the following sentences is punctuated correctly?

a

Ms. Lundquist, my second grade teacher, has written a very helpful book.
b

Ms. Lundquist my second grade teacher, has written a very helpful book.
c

Ms. Lundquist, my second grade teacher has written a very helpful book.
d

Ms. Lundquist my second grade teacher has written a very helpful book.

The correct sentence is:

a

Ms. Lundquist, my second grade teacher, has written a very helpful book.

The correct sentence with the correct punctuation is:

a

Ms. Lundquist, my second grade teacher, has written a very helpful book.