Because Web servers are platform and application (17) ，they can send or request data from legacy or external application including database．All replies，once converted into (18) mark up language，can then be transmitted to a (19) ．Used in this way，Intranets can (20) lower desktop support costs，easy links with legacy application and databases and， (21) all。ease of use．
A．abort
B．about
C．above
D．around