body {
    width:100%;
    margin: 0;
    padding: 0;
    background: #eff0f4;
}
.img-desktop {
    display: block;
}
.img-mobile {
    display: none;
}
.img-desktop img{
    width:100%;
}
.img-mobile img{
    width:100%;
}

@media (max-width: 767px)
{
    .img-desktop {
        display: none;
    }
    .img-mobile {
        display: block;
    }
}