Harder Riddle: The pebbles(Easy/Medium)

“Off with your head!”

The Queen of Hearts sentenced Alice to death again.

So as not to appear unfair, Her Majesty gives Alice one chance to save herself.

The ground is covered in tiny red and black pebbles. The Queen pretends to pick one of each colour, and puts them into a bag.

“If she pulls the red pebble from the bag, she shall go free!” Declared the Queen.

Alice has noticed the Queen’s trick – she has put two black pebbles into the bag.

How can Alice win her freedom without calling the Queen a cheater?