Concept:Antonyms are words with opposite meanings. The word "approve" means to give formal acceptance or agreement.
Explanation:"Approve" means to officially accept or agree to something. Its opposite is to refuse or not accept.
"Reject" means to refuse to accept or consider something. This is the direct opposite of approve.
The other options are synonyms or related words:
"Sanction" means to give official permission.
"Endorse" means to publicly support.
"Certify" means to confirm as true.
Therefore, the correct antonym is "reject".
Answer:A. Reject