a) Calcium chloride is used to create the competent cells as treatment of cells with calcium chloride makes transient pores in the cell wall of recepient cells (mostly prokaryotic cells) making it permeable and allowing the passsage of foreign DNA insert into the cell. The cells after treatment with calcium chloride are called as competent cells. b) Antibiotics are the substances which are produced naturally by some living organisms so as to check the growth of other organisms. Mostly fungi and some prokaryotes produce it. Antibiotics are the pontential chemical which serve to inhibit the growth and infection of bacteria and therefore, are used in prevention and cure of bacterial infections. Solution a) Calcium chloride is used to create the competent cells as treatment of cells with calcium chloride makes transient pores in the cell wall of recepient cells (mostly prokaryotic cells) making it permeable and allowing the passsage of foreign DNA insert into the cell. The cells after treatment with calcium chloride are called as competent cells. b) Antibiotics are the substances which are produced naturally by some living organisms so as to check the growth of other organisms. Mostly fungi and some prokaryotes produce it. Antibiotics are the pontential chemical which serve to inhibit the growth and infection of bacteria and therefore, are used in prevention and cure of bacterial infections..