1. Although everything seems to have been taken into consideration, ______ accident can happen when the astronauts walk in ______ space.
A．/; the B．an; the
C．the; the D．an; /
2. Sometimes advertisements make ______ possible for companies to sell the customers ______ money can not buy.
A．it ; that B．it; what
C．that; which D．it; whose
