A、A hunter. B、An old woman. C、A religious worker. D、A keeper of goats. D文中说主人注意到他的羊吃了一棵树上的小果子后变得非常兴奋和活跃，故答案为D。

Coffee is part of an international industry Research shows that as many as one-third of the people in the world drink coffee. But not everyone may know the story of coffee and how it is produced. One popular story about the discovery of coffee long ago is about Kaldi, (29)a keeper of goats. Kaldi was taking care of his goats in the highlands of Ethiopia where coffee trees had grown for centuries. (29)He noticed that his goats became very excited and active after eating small fruits from a tree. Kaldi reported this discovery to a group of religious workers. When they made a drink out of the fruit, the religious workers realized they could stay awake for long hours of prayer. Coffee trees can grow up to nine meters high, but they are cut short for production. The plant produces a fruit that is called a coffee cherry. When the coffee cherries are ripe and ready to be, picked, they are bright, red and firm. (30)Inside the fruits are the green coffee beans. After these beans are roasted at high temperatures they are ready to be made into a drink.There may only be two main kinds of coffee plants. (31) But geography and climate differences have a big effect on the many different ways coffee can taste. For example, coffee grown in Ethiopia is known for its lively, sharp taste and its flowery smell. Coffee from the island of Sumatra has a full body with an earthy and intense taste.