Cardi B Angrily Throws Pen After Asked About Offset-Stefon Diggs Triangle

2:53 PM PT -- Cardi B is pissed and she's letting the world know it, writing on X that she had to miss her kids first day of school to attend her civil trial.

Cardi B went from glowing to growling after leaving court on Tuesday after someone dared to ask if she was pregnant!!!

TMZ caught the wild exchange earlier today ... someone off camera asked if she would predict any paternity drama with Stefon Diggs -- in light of Offset apparently bragging he banged her up with Baby No. 4!!! 😬

Cardi didn't take kindly to the question coming from a guy outside the Alhambra, CA courthouse, and threw a pen in a fit of rage ... causing her bodyguard to call her back.

She retreated back to her vehicle but gave the guy a piece of her mind -- respect women or else!!!

Earlier today, Cardi dodged the pregnancy question as she made her way into the courtroom ... but still hasn't flat-out addressed the situation since the speculation started.