Final answer:
The correct 5-letter word for a ventriloquist's puppet is 'dummy.' It is a professional term in the context of ventriloquism, and the other options provided do not describe a ventriloquist's puppet.
Step-by-step explanation:
The correct term for a ventriloquist's puppet is indeed a dummy. The word dummy is a 5-letter term that is widely used to refer to the figure that a ventriloquist manipulates during a performance. Despite its other connotations in different contexts, when it comes to ventriloquism, dummy is the professional term and not considered rude. The other options provided, such as mirth, jest, and prank, do not correctly describe a ventriloquist's puppet. Mirth refers to amusement or laughter, jest is a joke or witty remark, and prank means a practical joke or mischievous act.