我国的万里长城、大运河和千里海堤被誉为“中国古代三大工程”，其中的千里海堤是指什么？

— You may have seen this film.—（）

A.I twas shown the next week

B.It is said to cos tmuch money

C.Actually,Ihaven’t seen it yet

D.You may have seen it too