B. The explanation for a downsloping aggregate demand curve differs from the explanation for the downsloping demand curve for a single product because a downsloping aggregate demand curve assumes constant money income such that a lower price causes a substitution of the now relatively cheaper product for those whose prices have not changed. aggregate demand curve assumes constant prices such that changes in income cause a substitution of a now relatively cheaper product for those whose prices have not changed. single-product demand curve assumes constant prices such that changes in income cause a substitution of a now relatively cheaper product for those whose prices have not changed. single-product demand curve assumes constant money income such that a lower price causes a substitution of the now relatively cheaper product for those whose prices have not changed. c. The multiplier causes an initial change in spending to generate an equal change in saving. causes an initial change in spending to generate an even larger change in the aggregate demand curve. reduces how spending changes influence the aggregate demand curve. equalizes the change in spending and the change in aggregate demand.