Plzz help. (1) Your dog makes too much noise at night. (2) Many of your neighbors cannot sleep he barks so much. (3) We have tried knocking on your door to speak with you, but there is never an answer. (4) Therefore, I am writing this letter to tell you about the problem. (5) Your dog is actually barking I am writing this letter. (6) Will you please get your dog to stop barking? Sincerely,

Your tired neighbor

Which linking word best fills the blank in sentence 2?
A.
so
B.
before
C.
because
D.
although