Momentum exception: or not

[GA Umpire]

I will try to get the Board back to football.

The following is causing discussion as to the correct answer.

Team A 3/5 from the B39 yard line.  Team A's pass is intercepted by B37 at the B4 yard line.  B37, after the interception, continues with momentum into the EZ and attempts to run out.  He is hit and fumbles.  The ball rolls into the field of play going OOB at the B6 yard line. During the attempted return B58 blocks below the waist at the B8 yard line.

         Which statement is TRUE:
      A.  This is a touchback. 
      B.  This is a safety.
      C.  Team B 1/10 at the B3 yard line.
      D.  Team B 1/10 from the B2 yard line

Any insight to the correct answer will be appreciated.  Rule reference, etc.
I cannot find a case play concerning the above situation.

[zoom]

This is clearly a Safety if the penalty is accepted under NFHS rules. (The result is different under NCAA rules).
The Momentum Exception is off because the ball left the end zone. (8-5-2 Exception). The foul occurred during B37's run (which includes the loose ball) so the basic spot for enforcement is the end of the run and in the end zone. Under All but One, that will be the enforcement spot. Since the enforcment spot is in the end zone, it is a safety. If the penalty is declined, it will be B 1/10 @ B-6. But, A will certainly accept the penalty. 10-3-3-b, 10-4-4, 8-5-2-c

In NCAA, since the forward fumble OOB is returned to the spot where the run ended, it never left the end zone and the Momentum Exception would still be ON. In that case, the end of the run would be the momentum spot, the B-4. Under 3 and 1, the penalty would be enforced from there and it would be 1/10 for B ay the B-2.