问题:

Look at this: http://www.consultacultura.it/portale_comunale_della_cultura.asp?IDcomune=1

Carousel images are not responsive like images under of it. They have the same class img-fluid.

回答1:

This is a known issue in Bootstrap 4 Alpha 6...

https://github.com/twbs/bootstrap/issues/21611

As a workaround you can use..

.carousel-item.active,
.carousel-item-next,
.carousel-item-prev {
  display: block;
}

http://www.codeply.com/go/0QUU06MiIL

回答2:

For me that workaround did not work for both, desktops and mobiles. I adjusted the proposed workaround a bit to make it -orientation- sensible.

@media (orientation: portrait) { 
    .carousel-item.active,
    .carousel-item-next,
    .carousel-item-prev {
        display: block;
        width:100%;
        height:auto;
    }
}

@media (orientation: landscape) { 
    .carousel-item.active,
    .carousel-item-next,
    .carousel-item-prev {
        display: block;
        width:100%;
        height:96vh;
    }
}