You take the word 'futile' and combine it with other words, at least one of which should be a verb, using the rules of grammar for the language in question.
Resistance is futile, human. Her wild attempts at explanation were futile.
Resistance is futile! The 'hail Mary pass' was a futile attempt to tie the score in the game's final seconds.
The word "futile" is an adjective. An example of a sentence using the word would be: Their attempt to fix the bridge had been futile, so they needed to find a different route.
Resistance is futile! His heroic effort turned out to be futile, after all.
It was futile to sit up waiting for Santa. Remember: he sees you when you're sleeping.
Resistance is futile!
Charlotte's effort to stop the car from rolling down the hill was futile. apex
The rescue mission was futile.
The bank robbers tried their best to escape the police chasing after them, but their attempt was futile, as they were soon apprehended and thrown in jail.
Most likely it means that not asking a question is pointless. Hence, it is futile not to ask the question.
Despite their efforts, their attempts to change the outcome were futile.
Futile is an adjective.