Menzel said bees' learning, like【81】of many animals, was based on a reward system. "If a bee is rewarded once for something, it remembers it for a week. But if it is rewarded three times, it will remember it for its【82】lifetime." Said Menzel. He last week was awarded a【83】by the German Zoological Society.
The memory capacity of bees means they can【84】among more than 50 different smells to find the one they want. "What is interesting is that what smells good to a bee, is also a【85】smell for humans. " said Menzel.
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A. working hard
B. hardworking
C. hard working
D. working hardly