A Medical Researcher Has Isolated a Chemical from Cigarette Smoke

A medical researcher has isolated a chemical from cigarette smoke.When the scientist mixes a small amount of the substance with living human cells,the chemical damages unsaturated fatty acids in the cells' plasma membranes.He is able to prevent this damage by adding vitamin E to the mixture of the chemical and cells.Based on this information,the scientist has _________.

A) determined that the chemical in cigarette smoke is an oxidizing agent
B) discovered a vitamin-based cure for lung cancer
C) conducted an in vitro experiment under poorly controlled conditions
D) identified vitamin E as a prooxidant