15. The production of recombinant DNA (DNA cloning) involves the following 4 steps. Step 1: Preparation of fragments of foreign DNA. Step 2: Insertion of foreign DNA fragment into a cloning plasmid. Step 3: Introduction of recombinant DNA into a recipient cell for replication. Step4: Selection of cells containing the correct recombinant DNA. Among them, step （Ａ） involves PCR reaction and step （B） usually requires the use of antibiotics. （Ａ） and （B） correspond to (A) 1 and 3 (B)2 and 4 (C) 1 and 4 (D) 2 and 3 (E) 3 and 4