一个do-while循环不断说同样的事情

Question

为什么这个循环总是说＆＃34;选择＆＃39;或者＆＃39; h＆＃39;再试一次＆＃34;当我选择＆＃39;或者＆＃39; h＆＃39;？我觉得逻辑是正确的我只是不知道它说无论我把它放在哪里，即使它是＆＃39; s＆＃39;或者h＆＃39;。

do {
    printf("Do you want to (H)it or (S)tand?");
    scanf("%ch", &decision);
    tolower(decision);
    if (decision != 'h' && decision != 's') {
        printf("Pick 's' or 'h'. Try again.\n");
        printf("Do you want to (H)it or (S)tand?");
        scanf("%ch", &decision);
        tolower(decision);
    }
    if (decision == 'h') {
        playershand = add_card_to_hand(&playershand, card);
        printf("Your cards:\n");
        print_hand(playershand);
        playerscore = blackjack_value(playershand);
        printf("Score = %d\n", playerscore);
    }
    if (decision == 's') {
        add_card_to_hand(&dealershand, card);
        print_hand(dealershand);
    }