Which of the following statements about Nibbana/Nirvana are true? A) Nibbana is the destruction of the defilements.
B) Nibbana is merely the destruction of defilements.
C) Nibbana is an existing reality that is subjected to the mind totally free of defilements.
D) Nibbana is an existing reality that destroys the defilements in the mind as a result of being the object of Samma Samadhi(Right Concentration) 
E) Nibbana is an existing reality that is subjected the mind free of certain defilements.
F) Nibbana is an existing reality that is subjected to the mind when the defilements are subdued.


Nibbana is said to be uncaused. So it should be already existing, even before the defilements are removed. That makes the statement 'B' invalid in my opinion.
Nibbana is actually best understood as the cessation of suffering. The lakkhanadicatuka for nibbana is as follows (minus proximate cause because it is uncaused):


  It has peace as its characteristic. Its function is not to die; or its function is to comfort.  It is manifested as the signless; or it is manifested as non-
  diversification.
  
  -- Path Of Purification XVI.66


The relationship between nibbana and the defilements is not direct; it is the noble path that destroys the defilements, not nibbana itself. Even though the suttas say that nibbana is destruction, this is not technically true:


  69.[Q. 5] But is not Nibbāna destruction, because of the passage beginning,“That, friend, which is the destruction of greed … [of hate
  … of delusion … is Nibbāna]?” (S  IV 251).
  
  [A.] That is not so, because
  it would follow that Arahantship also was meredestruction. For that
  too is described in the [same] way beginning, “That, friend, which is
  the destruction of greed … of hate … of delusion … is Arahantship]” (S
  IV 252).
  
  -- Path Of Purification XVI.69


The point is that nibbana itself is not destruction, but the attainment of nibbana (and arahantship) brings about the destruction of the defilements. 

So A), B), and D) are technically incorrect.

As for C), E), and F), nibbana is an existing reality, but it is not subjected to anything, even the mind. The mind takes nibbana as an object during an experience of cessation, but this too has nothing directly to do with the defilements, which have been abandoned from the first moment of cessation (path consciousness). Therefore, if I am understanding these three statements correctly, they too are not correct.