Query posts from category A, and from either category B or C

Not sure this is the best way, but I have managed to get the desired result set with following $args parameters.

$args['tax_query'] =    array(
    'relation' => 'AND',
    array(
        'taxonomy' => 'category',
        'field'    => 'id',
        'terms'    => array(100),
    ),
    array(
        'taxonomy' => 'category',
        'field'    => 'id',
        'terms'    => array(105,106),
    ),
);