複選題24. Regarding molecular cloning using restriction cnzyme and ligase. Which of the following statement is correct? (A) Blunt end is clean and thus easier to be ligated. (B) Two sticky ends with complementary overhangs can be perfectly ligated and a restriction enzyme recognition site must be restored. (C) Restriction enzyme more efficiently cuts at the ends of DNA fragments. (D) Phosphatase treatment of both digested vector and digested insert reduces self- ligation so that correct ligation is enhanced. (E) Ligase also mediates joining of sticky ends by catalyzing the formation of phosphodiester bonds.