18.Had you informed me of the problem, I ______ assistance.
(A) would has provided (B) would had provided
(C) would have been provided (D) would have provided
28.A: The soles of your shoes look worn out. B: I just bought them last month. ______ (A) They were on sale. (B) The shoes are made from high-quality leather. (C) Do you like how they look? (D) They must have cut corners during production.