Answer is
❌. A. In order to keep the party a surprise, we
had to conceit our identities.
The correct word in place of conceit would be conceal ( to hide). Conceit means overly proud or vain.
These two are correct.
✅. B. That boy's intense conceit made it very
hard to get along with him.
✅ C. Emma was a very hard working girl, but
her conceit lost her a lot of jobs.