``` <?php $marks = array( "Ankit" => array( "C" => 95, "DCO" => 85, ), "Ram" => array( "C" => 78, "DCO" => 98, ), "Anoop" => array( "C" => 88, "DCO" => 46, ), ); $mark =["C" => 88, "DCO" => 46]; if(array_key_exists('Anoop',$marks)){ //检查数组中此键名是否存在； unset($marks['Anoop']['C']); } var_dump($marks); ?> unset($marks['Anoop']['C']); ```