Hi, I feel so confused about this question, can you give me a detailed answer for this question?

Consider a two period repeated game with the following stage game. 1 i 2 C D C 5. 2 D m This stage game is played twice and the repeatedgame payoffs are simply the sum of the payos in each of the two periods. A strategy of each player is to choose one of C and D in stage 1r 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 eguilibn'um of this game? 0 a. Strategy of player 1: Play 0 in stage 1; in stage 2. playr D it ((3,0) is played in stage 1 and play C othemrise Strategy of player 2: Play C in stage 1; in stage 2. playr D. O b. Strategy of player 1: Play 0 in both stages Strategy of player 2: Play 0 in both stages 0 c. Strategy of player 1: Play D in both stages Strategy of player 2: Play D in both stages 0 d'Strategy of player 1: Play C in both stages Strategy of player 2: Play D in both stages