Before Ehrlich began a systematic search for a chemical to kill specific bacteria,the only chemotherapies available were substances derived from medicinal plants.What distinguished Ehrlich's chemotherapy research

A)Ehrlich systematically tested hundreds of compounds for their ability to destroy specific bacteria without damaging surrounding tissue.
B)Ehrlich used metals,such as antimony and mercury to treat diseases.
C)Ehrlich inoculated his own son with fluid from a cowpox blíster.
D)Ehrlich introduced cinchona tree bark,a native American remedy to treat malaria.