Concept:An antonym is a word opposite in meaning. "Commend" means to praise formally or express approval. Its opposite should express disapproval or fault-finding.
Explanation:The word "commend" means to praise or approve in a formal way.
For example, a teacher commends a student for good work.
Now, we look for the opposite meaning among the options.
"Praise", "Approve", and "Applaud" all show positive appreciation — they are synonyms of "commend", not antonyms.
"Criticize" means to point out faults or express disapproval, which is directly opposite to praising.
Hence, the antonym of "commend" is "criticize".
Answer:C. Criticize