什么是 underpart？underpart是part
什么是 part？
- A lower part or a portion of a lower part or underside, especially of an animal's body: We recognized the robin by its reddish underparts.Una part inferior o una porció d'una part inferior o part inferior, especialment del cos d'un animal: Reconeixíem la túnica per les seves parts inferiors vermelloses.
- A subordinate role, as in a play.--