@import url(https://fonts.googleapis.com/css?family=Montserrat);

*{font-style: normal; font-family:'https://fonts.googleapis.com/css?family=Montserrat:400,700' rel='stylesheet' type='text/css'>: sans-serif: arial;background-color:whitesmoke; margin-bottom: 1px}

a{font-family:'https://fonts.googleapis.com/css?family=Montserrat:400,700' rel='stylesheet' type='text/css'>: sans-serif: arial;background-color:whitesmoke; margin-bottom: 1pxsans-serif;color:#57e535;text-decoration: none;font-style:italic;}

* {
    box-sizing: border-box;
}

    <style> 
* {

    box-sizing: border-box;
    list-style: none;
    margin: 0;
    padding: 0;
}

body {
    font-family: "montserrat", arial, helvetica, sans-serif;
    margin: 0;
    padding: 0;
}


a {
    text-decoration: none;
}

#contenedor { 
    margin: auto;
    max-width: 75em;
    min-height: 100vh;
    width: 90vw;
}

nav ul ul {
	display: none;
}
nav ul li:hover>ul {
	display: block;
}

.navigation {
  list-style: none;
  margin: 0; 
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  
  -webkit-flex-flow: row wrap;
  justify-content: space-between;
}

.navigation a {
  text-decoration: none;
  display: block;
  padding: 1em;
  color: #f0f3f2;
}

/****************************************

             3º: mediaqueries
 
(cambios en el layout en la medida en que
la ventana del navegador se va ensanchando)

*****************************************/


/* a partir de 320px */

@media screen and (min-width:20em) {

    nav ul{
        padding: 2em;
        /*  para que sea horizontal
            definimos la lista menú
            como caja flexible */
        display: -webkit-box;
        display: -webkit-flex;
        display: -ms-flexbox;
        display: flex;
        align-content: space-between;
    }
    nav ul li {
        /*  para que el menú se extienda a lo ancho
            definimos que sus "hijos" puedan crecer o achicarse */
        -webkit-box-flex: 1;
        -webkit-flex: 1;
        -ms-flex: 1;
        flex: 1;
        align-content: space-between;
        position:relative;
        list-style-type: none;
    
    }


a:hover {
   color: magenta;
}

h1{
    color:#57e535; 
    font-weight:100; 
    padding: 1em 0 0 0;
    text-decoration: underline; 
    text-align: center;
    letter-spacing: 0.2rem
}

h2 {
    font-size: 20px;
    color: magenta;
    text-decoration: underline
    
}
    

#contenedor {
    background-color: #eadcea;
    box-shadow: 0 0 0 1em rgba(0,0,0,0.1);
    margin: auto;
    max-width: 67.5em;
    min-height: 100vh;
    width: 90vw, 
}

   
.materias {
    display: block;
    display:inline-block;
    justify-content: center;
    align-items: center;
    border-color: #57e535;
    margin-left: 30em;
    margin-right: auto;
    margin-top: 2em; 
    font-size: 16px;
    list-style-type: none
    
}
    
    .materias ul li{
        color:#57e535;
        text-decoration: none;
           list-style:circle;
        margin-right: auto;
    }

#foto {
    display: block;
    margin: auto;
    width: 200px;
    height: 200px;
    border-radius: 150px;
    -webkit-border-radius: 150px;
    -moz-border-radius: 150px;
    }
    
    .presentacion {
        display: block;
        justify-content: center;
        margin-left: 26em;
        font-size: 15px;
        font-style: normal;
        
    }
    
    footer h5 {
    text-align: center;
    padding: 1em;
        margin-left: 15em;
        margin-right: 15em
}