Which is a valid Cisco CRS 4.0 deployment scenario? （）
A. redundant Cisco CRS Engines and a simplex database server
B. redundant Cisco CRS Engines with five simplex VoIP monitoring servers
C. redundant Cisco CRS Engines and databases running on two different nodes outside of the Cisco CRS cluster
D. redundant Cisco CRS Engines and databases with two VoIP monitoring servers and three recording server
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