GMAT Sentence Correction (SC) | Re: The principal feature of the redesigned checks is a series

Re: C, you can also think of it this way:

The underlined information is a list modifying "instructions" -- it explains what the instructions serve to do.

If the clause "that the company hopes will help merchants confirm a check's authenticity" is eliminated, it becomes easier to see how the modification works:

The principal feature of the redesigned checks is a series of printedinstructions....including reminders to watch the endorsement, compare signatures, and view
...

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