Final answer:
Option (b), To stimulate urination in sheep, rubbing a warm, wet cloth on the ventral abdomen serves as an effective method by providing an external stimulus similar to the "ram effect", which is used to induce ovulation.
Step-by-step explanation:
The method that can be used to stimulate urination in sheep is rubbing a warm, wet cloth on the ventral abdomen. This process can be likened to the expression by an external stimulus, similar to how the "ram effect" induces ovulation in sheep via the introduction of a ram.
The external stimulus in the case of inducing urination is the warm, wet cloth, which may potentially stimulate the nerve endings near the bladder and trigger the reflex to urinate. In context with reproductive behaviors, stimulation may also relate to hormonal changes, such as those observed when nutrients and hormones are delivered using a feeding tube, and during sexual behavior when the cl_itoris is stimulated.