Change code to random sort

plz I want to change the code

<div class="properties-filter-sort-by-wrapper">
    <select class="form-control" name="filter-sort-by"> 
        <option value=""><?php echo __( 'Sort by', 'realia' ); ?></option> 
        <option value="price" <?php if ( ! empty( $_GET['filter-sort-by'] ) && 'price' == $_GET['filter-sort-by'] ) : ?>selected="selected"<?php endif; ?>><?php echo __( 'Price', 'realia' ); ?></option>                                
        <option value="title" <?php if ( ! empty( $_GET['filter-sort-by'] ) && 'title' == $_GET['filter-sort-by'] ) : ?>selected="selected"<?php endif; ?>><?php echo __( 'Title', 'realia' ); ?></option>                       
        <option value="published" <?php if ( ! empty( $_GET['filter-sort-by'] ) && 'published' == $_GET['filter-sort-by'] ) : ?>selected="selected"<?php endif; ?>><?php echo __( 'Published', 'realia' ); ?></option>                          
    </select>
</div>

And replace by defalut to random and if possible to hide (Sorting options and Order) tanks to all