Which of the following ways is correct to Set the media query ? code example

Example 1: media query in css

@media screen and (min-width: 374px){
   section#rent_sectionn {
    padding: 0 20px !important;
}
 }

Example 2: media query in html style

span { background-image: url(particular_ad.png); }

@media (max-width: 300px) {
    span { background-image: url(particular_ad_small.png); }
}