div{
    font-size:140%;
}

/*
https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors
*/

/*Select all <div> elements with an class begin with "d-", case-insensitive*/
div[class^="d-"]{
    border: 1px solid black;
    margin-top:3%;
}

/*Select all <div> elements with an class containing "d-lg-block", case-insensitive*/
div[class*="d-lg-block"]{
    color:red;
}
div[class*="d-md-block"]{
    color:blue;
}
div[class*="d-sm-block"]{
    color:green;
}