If you’re the player answering the yes-or-no question, you must abide by your answer if able. For example, if you are asked “Is the Slaying Mantis you control going to attack on your next turn?” and you say yes, then it must attack if able. However, if it’s tapped as you declare attackers that turn, then you aren’t able to attack with it, and you don’t have to abide by your answer.

Frankie Peanuts hates snitches, but he detests unsporting conduct. Keep your questions appropriate for your game and its surroundings.