供需

gōng xū supply and demand

原理

yuán lǐ principle; theory

哪

nǎ how; which

na (particle equivalent to 啊 after noun ending in -n)

něi which? (interrogative, followed by classifier or numeral-classifier)

种

zhǒng seed; species; kind; type; classifier for types, kinds, sorts

zhòng to plant; to grow; to cultivate

快

kuài rapid; quick; speed; rate; soon; almost; to make haste; clever; sharp (of knives or wits); forthright; plainspoken; gratified; pleased; pleasant

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