You should Remove Query String from Static Resources in order to boost your wordpress site’s performance and Google PageSpeed performance grade as well.

Tips:

https://tools.pingdom.com/ this tool will tell you tell which aspect to improve just type in your site url and then click on Start Test

This option is recommended for Pro users. You need to add following code in your theme’s function.php file.

/*** Remove Query String from Static Resources ***/
function remove_cssjs_ver( $src ) {
 if( strpos( $src, '?ver=' ) )
 $src = remove_query_arg( 'ver', $src );
 return $src;
}
add_filter( 'style_loader_src', 'remove_cssjs_ver', 10, 2 );
add_filter( 'script_loader_src', 'remove_cssjs_ver', 10, 2 );