40. A series of experiments to test the new drug _______ carried out, but so far it still can’t prove to be an
effective drug.
(A) was (B) were (C) has been (D) have been
51. “Susan hasn’t told you about her resignation, has she?” Choose the best response.
(A) Yes, she did. (B) Yes, she hasn’t. (C) No, she has. (D) No, she hasn’t.
55. The departure dates listed in this brochure for the summer tours _______ change.
(A) look up to (B) look forward to (C) are subject to (D) are based on