Past simple/Past subjunctive

[sapuna]

Before it will be made available to the public, the painting was sold to a private collector and is currently on hold at the auction house awaiting pick-up.

A) Before it will be made available to the public
B) Before it can be made available to the public
C) Before it could be made available to the public
D) Before it has been made available to the public
E) Before it was made available to the public

I marked E . However, answer C is given as the correct one. Can somebody explain why ? I thought wordier sentances ( like answer choice C ) are usually wrong

[whitehalo]

The grammar issue tested here is verb time sequences.

'Before it will be made available to the public' indicates an event that would have also happened in the past, but the future tense 'will be' is wrong.

'the painting was sold' is an event that happened in the past, and therefore, we need a subjunctive construction 'could be'. 'was' is in simple past tense which is wrong because the event of being 'made available to the public' did not actually happen.

[theCodeToGMAT]

{A} INCORRECT; "will" is future.. we need some past verb.
{B} INCORRECT; "can be" is present.. we need past verb
{C} CORRECT
{D} INCORRECT: "has been" is wrong tense
{E} INCORRECT; two past events must be in perfect tense.