Choose the sentence with the correct punctuation.

a.
I have a truckload of homework, therefore I will not be able to go to the movies.
b.
I have a truckload of homework; therefore, I will not be able to go the movies.
c.
I have a truckload of homework therefore I will not be able to go to the movies.
d.
I have a truckload, of homework, therefore; I will not be able to go to the movies.