Choose the correct form of verb:
(1) They ______ here a month ago
(A) come
(B) will come
(C) comes
(D) came
(2) Sohan was _______ by a dog.
(A) had bit
(B) bite
(C) bitten
(D) bit
(3) The teacher ________ English for twenty years.
(A) teach
(B) is teaching
(C) has been teaching
(D) have been teaching