Which one of the following is NOT a subgameperfect equilibrium of this game?

Consider a two period repeated game with the following stage game. 1/2 C D C 5,2 1, 1 2 DIN-.3 This stage game is played twice and the repeated-game payoffs are simply the sum of the payoffs in each of the two periods. Astrategy of each player is to choose one of C and D in stage 1, and for each possible outcome of stage 1, choose one of C and D in stage 2. Which one of the following is NOT a subgame perfect equilibrium of this game? A a. Strategy of player 1: Play C in stage 1; in stage 2, play D if (0,0) is played in stage 1 and play C othenivise. Strategy of player 2: Play C in stage 1; in stage 2, play D. -A b. Strategy of player 1: Play C in both stages Strategy of player 2: Play C in both stages A c. Strategy of player 1: Play D in both stages Strategy of player 2: Play D in both stages if? d' Strategy of player 1: Play C in both stages Strategy of player 2: Play D in both stages