· The underlined word is "vouch," which means to confirm or certify something as true or effective. The word opposite in meaning would imply denial or disapproval.
· Invalidate implies making something void, ineffective, or worthless. It is the correct opposite here.
· Other options:
o Maintain means to uphold or keep in good condition (unrelated).
o Certify means to confirm or verify something (unrelated).
o Witness means to see or observe (unrelated).
Thus, the opposite meaning of "vouch" in this context is invalidate.
Hence, option (c) is the answer.
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