An organization has contracted with a vendor for a turnkey solution for their electronic toll collection system (ETCS). The vendor has provided its proprietary application software as part of the solution. The contract should require that: 
A、a backup server be available to run ETCS operations with up-to-date data. 
B、a backup server be loaded with all the relevant software and data. 
C、the systems staff of the organization be trained to handle any event. 
D、source code of the ETCS application be placed in escrow.