be doing sth.
be always doing sth .
be doing sth.when
be worried doing sth 还是be worried about doing sth
be successful in (doing) sth.be successful at (doing) sth.
be worth sth./doing sth.造句,
be worthy of sth / doing sth.
be busy doing sth/with sth
be interested in doing sth
be used to doing sth?
be due to doing sth.
be long in doing sth
be busy in doing sth