【单选题】Both Blu-ray (and/ in addition ) HD-DVD devices are backward-compatible with current CDs and DVDs, meaning you can play your old discs on the new players.
【简答题】A.They would help the crew to get out of the desert. B.They would help the crew to have radio contact. C.They would help people to identify them. D.They would help the engineers to know what had befal...