.wrong{
    position: relative;
}
.wrong:before{
    content: '';
    display: block;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: #f00;
    opacity: 0.3;
}
.question1 .wrong:before,.question2 .wrong:before,.question3 .wrong:before,.question5 .wrong:before,.question7 .wrong:before{
    border-radius: 50%;
    top: 5%;
    left: 5%;
    width: 90%;
    height: 90%;
}