Correct Answer: A loud and unrestrained laugh.

Solution : The correct choice is the third option .

The idiom belly laugh refers to hearty, deep, and unrestrained laughter that comes from the abdomen or belly, expressing genuine amusement or joy. It signifies a loud, robust, and often contagious form of laughter that is wholehearted and sincere, which is quite similar to what is given in the third option.