What is the main purpose of undertaking a parallel run of a new system?
A.
Resolve any errors in the program and file interfaces
B.
Verify that the system provides required business functionality
C.
Validate the operation of the new system against its predecessor
D.
Provide a backup of the old system
This same question posted at another site has C as the correct answer:
http://www.allinterview.com/showanswers/14952/primary-purpose-undertaking-parallel-run-new-system-verify-provides-required-bus.html
It makes no sense to specify a parallel run if you do not compare old and new.
Validating business functionality requires a run but not necessarily a parallel run.
so I vote for C.