styles.css

.que.oumultiresponse .answer .specificfeedback {
    display: inline;
    padding: 0 0.7em;
    background: #fff3bf;
}
.que.oumultiresponse .answer div.r0,
.que.oumultiresponse .answer div.r1 {
    display: flex;
    flex-wrap: wrap;
    align-items: baseline;
}
.que.oumultiresponse .answer div.r0 label,
.que.oumultiresponse .answer div.r1 label,
.que.oumultiresponse .answer div.r0 div.specificfeedback,
.que.oumultiresponse .answer div.r1 div.specificfeedback {
    /* In Chrome and IE, the text-indent above is applied to any embedded table
       cells or <li>s, which screws up the intended layout. This fixes it again. */
    text-indent: 0;
}

.que.oumultiresponse .answer div.r0 label,
.que.oumultiresponse .answer div.r1 label {
    flex: 1 1;
}

.que.oumultiresponse .answer div.r0 div.specificfeedback,
.que.oumultiresponse .answer div.r1 div.specificfeedback {
    display: flex;
    flex: 1 1 100%;
}

.que.oumultiresponse .answer div.r0 input,
.que.oumultiresponse .answer div.r1 input {
    margin: 0 5px;
    padding: 0;
    width: 15px;
}

.que.oumultiresponse .answer div.r0 span.answernumber,
.que.oumultiresponse .answer div.r1 span.answernumber {
    white-space: nowrap;
}

/* Fix positioning of icons in Moodle 3.5+. */
.que.oumultiresponse .answer div.r0 .icon.fa-check,
.que.oumultiresponse .answer div.r1 .icon.fa-check,
.que.oumultiresponse .answer div.r0 .icon.fa-remove,
.que.oumultiresponse .answer div.r1 .icon.fa-remove {
    text-indent: 0;
}

/* Editing form. */
/* Top */
body#page-question-type-oumultiresponse div[id^=fitem_id_][id*=answer_],
body#page-question-type-oumultiresponse div[id^=fitem_id_][id*=hint_] {
    background: #eee;
    margin-top: 0;
    margin-bottom: 0;
    padding-bottom: 5px;
    padding-top: 5px;
    border: 1px solid #bbb;
    border-bottom: 0;
}

body#page-question-type-oumultiresponse div[id^=fitem_id_][id*=_answer_] .fitemtitle,
body#page-question-type-oumultiresponse div[id^=fitem_id_][id*=hint_] .fitemtitle {
    font-weight: bold;
}
/* Middle */
body#page-question-type-oumultiresponse div[id^=fitem_id_][id*=correctanswer_] {
    background: #eee;
    margin-bottom: 0;
    margin-top: 0;
    padding-bottom: 5px;
    padding-top: 5px;
    border: 1px solid #bbb;
    border-top: 0;
    border-bottom: 0;
}
/* Bottom */
body#page-question-type-oumultiresponse div[id^=fitem_id_][id*=feedback_],
body#page-question-type-oumultiresponse div[id^=fgroup_id_][id*=hintoptions_] {
    background: #eee;
    margin-bottom: 2em;
    margin-top: 0;
    padding-bottom: 5px;
    padding-top: 5px;
    border: 1px solid #bbb;
    border-top: 0;
}

body#page-question-type-oumultiresponse div[id^=fitem_id_][id*=penalty] {
    margin-bottom: 2em;
}