In a female pig, the urethra, and the vagina unite to form the ________.

A) vulva
B) urogenital sinus
C) genital papilla
D) urogenital orifice

In female pigs, the urethra and vagina unite to form the urogenital sinus, which is the common opening for both the urinary and reproductive tracts. The vulva (A) is the external opening of the female reproductive tract, while the genital papilla (C) is a protrusion that covers the urogenital sinus in young female pigs, which later disappears as the animal matures. The urogenital orifice (D) is a general term that refers to the opening where urine and/or reproductive cells exit the body.