GRE Reading Comprehension: ETS Official Practice 150-GRE OP150: 阅读 - 9K44UV63AUO4X5L31

That sales can be increased by the presence of sunlight within a store has been shown by the experience of the only Savefast department store with a large skylight. The skylight allows sunlight into half of the store, reducing the need for artificial light. The rest of the store uses only artificial light. Since the store opened two years ago, the departments on the sunlit side have had substantially higher sales than the other departments.