Please explain the slow step because it still confuse me

Please read about mechanisms on pages 625633 in your text book. Then solve the following problem. 23. The complete mechanism for a reaction is considered to occur in two steps, one of which is slow and the other fast: A+BCA+CD+Efastslow What is the rate law predicted by this mechanism? a) Rate =k[A][B] b) Rate =k[A][C] c) Rate =k[A]2[B] d) Rate =k[A][C]2 e) Rate =k[A]2[B][C] Answer Explanation