Question

rough strain nonvirulent smooth strain virulent heat-killed smooth strain rough strain & heat-killed smooth strain mouse lives mouse dies mouse lives mouse dies why did griffith use heat to kill the pneumonia-causing bacteria? to test the effects of mixing strains because the experiment was over because he had no other choice

Explanation:

Griffith's experiment aimed to study bacterial transformation. Heating the smooth (virulent) strain killed the bacteria, making them non - virulent on their own (as seen when the heat - killed smooth strain alone didn't kill the mouse). Then, when mixed with the rough (non - virulent) strain, the heat - killed smooth strain could transfer genetic material to the rough strain, making it virulent. So the purpose of heating was to test the effects of mixing strains (by inactivating the virulent strain to see if its genetic material could still act when mixed with another strain). The other options are illogical: the experiment wasn't over, and he had choices in experimental methods.

Answer:

A. to test the effects of mixing strains