middlegame chess study

White to move and win.  Is the key to the win:   A) Rf7 or B) Rg4 or C) Kf3 or D) Ra5?

--Since the chessboard has 32 men at start, let us say the endgame begins when there are 1/3 of men left on the board, and middlegame begins when there are 2/3 of men left on the board.  This study has 12, so it appears to fall into endgame section (3-12 men), in contrast to middlegame which has from 13-22 chessmen on the board, and contrasting opening section which has 23-32 men.--  

Why I won't put the solution to this study on this page--I got bored with doing all the work for those who supposedly would like to learn chess.  I gave a big clue:  4 likely moves.  I didn't solve this by using a computer.    -well, that part changed:
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6-23-17 UPDATE:  stockfish 6 claims at depth 20 that A) is correct, giving it 1.25 pawn advantage.  Move D) in contrast has only .4 pawn advantage according to stockfish 6.  I did not choose A) myself.  As for C) this line as played by stockfish went to a draw as did moves A) and D).  Then I tried another possiblility, E) Rgg5 which also went to draw by stockfish.  I ran it at depths 20-26.