_____,the disease diphtheria would produce a powerful poison that would kill the patient.

A. If it untreated         B. If untreated           

C. To be untreated      D. It being untreated

People in Nome all had diphtheria, a disease that spreads very fast. If ________, it would produce a powerful poison that would kill the patient.

A. untreating        B. to untreat        C. untreated         D. untreat