A.
Deontology is an ethical principle claiming that an action is morally right or wrong based on its adherence to a moral code, or rule, regardless of the consequences of the action. In a classic example, according to deontology, lying is always wrong, no matter what, because it breaks a moral rule. Even if a lie will make someone feel better or even save a life, it is still wrong to lie.
In this case, option A is the only counterargument that factors in specific moral codes, I.E, the Hippocratic Oath. This oath essentially boils down to "do no harm". By taking the oath literally, helping a patient die or giving them the means to help them die, is considered doing harm. Regardless of how the patient or family feels, it is always wrong because it breaks a moral code. This is consistent with the concept of deontology.