Final answer:
A pudendal nerve block anesthetizes the perineum and external genitalia, and does not affect the lower extremity, abdominal area, or the chest and back.
Step-by-step explanation:
A pudendal nerve block provides anesthesia over the perineum and external genitalia (Option C). This type of nerve block specifically targets the pudendal nerve, which is responsible for the sensory and motor supply to the pelvic floor, including the deep muscles of the perineum, muscles surrounding the anus, and structures such as the bulbourethral gland and membranous urethra. The pudendal nerve block does not provide anesthesia to the entire lower extremity, abdominal area, or the chest and back. It is performed by injecting a local anesthetic near the pudendal nerve, which supplies sensory and motor innervation to the perineum and external genitalia.