Final answer:
The mandibular 2nd premolar has three rounded cusps on the lingual surface and is used for mashing foods.
Step-by-step explanation:
The mandibular 2nd premolar has three cusps on the lingual (tongue) surface. The lingual cusps are rounded and are used for mashing foods. This tooth is located posterior to the cuspids (canines) and is part of the premolar group.