The Following Passage Contains an Argument That Is Somewhat Complex

The following passage contains an argument that is somewhat complex, either because it makes complicated claims or contains a lot of supplementary information. Identify the best standard-form representation of the argument.
The passage: In the past, a common definition used to determine if someone was dead was this: a person is dead if, but only if, they were not respirating and their blood was not circulating. Call this the cardiopulmonary definition of death. It turns out that this definition of death is implausible. This becomes clear when we contemplate cases where a person's brain is irreversibly damaged so that it no longer functions at all. A patient in this condition could be put on an artificial respirator and thus would be respirating. The cardiopulmonary definition classifies a person whose brain is entirely non-functional as not dead. The cardiopulmonary definition is therefore implausible, since a person with no brain function clearly should be classified as dead.

A) 1) If a person's brain is irreversibly damaged so that it no longer functions at all, that person is not dead.
2) The cardiopulmonary definition of death implies that a person is dead if their brain has lost all function.
So, the cardiopulmonary definition of death is implausible.
B) 1) According to the cardiopulmonary definition of death, a person is dead if, but only if, they are not respirating and their blood is not circulating.
2) The cardiopulmonary definition of death is implausible.
So, a person whose brain is entirely non-functional is dead even if they're respirating.
C)
1) If the cardiopulmonary definition of death is true, then a person with irreversible loss of all brain function is not dead if they're breathing on an artificial respirator.
2) But a person with irreversible loss of all brain function is dead even if they're breathing on an artificial respirator.
So, the cardiopulmonary definition of death is not true.
D) 1) A person is dead if, but only if, they are not respirating and their blood is not circulating.
2) A person whose brain has irreversibly lost all function but is on an artificial respirator is respirating.
So, a person whose brain has irreversibly lost all function but is on an artificial respirator is not dead.