<picture>
<source srcset="/img/mainpage_mainimg_3_576w.jpg 576w, /img/mainpage_mainimg_3.jpg 1920w" />
<img class="carousel-item__img d-block" src="/img/mainpage_mainimg_3.jpg" sizes="100vw" alt="Первый слайд">
</picture>
<picture>
<source media="(min-width: 650px)" srcset="img_pink_flowers.jpg">
<source media="(min-width: 465px)" srcset="img_white_flower.jpg">
<img src="img_orange_flowers.jpg" alt="Flowers" style="width:auto;">
</picture>