Final answer:
The correct synonym for 'is certainly no time to "fib"' is 'There is definitely no time to "lie".' 'Lie' is synonymous with 'fib,' which means to tell a small lie.
Step-by-step explanation:
The synonym for the phrase 'is certainly no time to "fib"' is 1) There is definitely no time to "lie". The word "fib" is a colloquial term that means to tell a small or trivial lie. Therefore, the term that is synonymous with "fib" in this context is "lie", which means to tell an untruth or to deceive. Companion phrases that evoke a similar challenge to authenticity such as "Are you for real?", "Really!", and "No kidding!" question the veracity of a statement but do not imply deceit outright as "fib" does.