In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Passage: The crew of a malfunctioning alien cargo ship make an emergency landing on Earth. This draws the attention of four sexually-frustrated humans in a nearby park: Oliver and Prudence (a mild-mannered professional and his highly-strung fiancée), Willy (a bumbling shop assistant) and Cliff (a middle-aged man).
Oliver, Prudence, Willy and Cliff wander into the ship and encounter three aliens resembling human women: engineer Partha, nurse Cosia and the captain, known only as Skipper. Willy inadvertently drops some pornographic magazines that he has recently bought. The aliens mistake some approaching cows for a hostile force and hurriedly take off, despite warnings from the long-suffering computer about the precarious state of the ship's systems. Resuming their original course, they study their guests in detail. Fascinated by the anatomy of the males, they decide to sell them to a zoo for exotic lifeforms on a distant planet. They also debate the significance of the acts depicted in Willy's magazines. Partha is particularly keen to emulate them and enthusiastically has sex with Cliff.
Skipper, Cosia and Partha subject the males to a series of tests to learn more about their abilities. Oliver and Cliff fail miserably. However, Willy, looking for his magazines, beats Skipper's combat simulation by unknowingly evading her attacks, causing her to collapse with exhaustion and infer that he is a stronger being. While conducting a physical examination on Willy, Cosia discovers that his biology is more advanced than anything known to their species; encouraging Cosia with exaggerated claims about his sexual prowess, Willy loses his virginity to her. Later, he passes an intelligence test by a fluke and has sex with Partha.
Who mistakes some approaching cows for a hostile force?