A.前者說(shuō)明投資的變化對(duì)國(guó)民收入的影響,后者說(shuō)明國(guó)民收入的變化又對(duì)投資產(chǎn)生影響; B.兩者都說(shuō)明投資是怎樣產(chǎn)生的; C.前者解釋了經(jīng)濟(jì)如何走向繁榮,后者說(shuō)明了經(jīng)濟(jì)怎樣走向蕭條; D.A和C