VOA慢速英语:Changing Gene in Plant Could Yield More Crops

exhausted – adj. completely used up

biological clock – n. a system that controls natural processes such as waking, sleeping and aging

yield –  n. the amount of something that is produced by a plant or farm

manipulate – v. to use or change for a particular purpose

in tune with  – (idiom; figurative) to be in agreement with someone or something

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