参考答案：A

解析：

Because we assume money wages and resource prices to be constant in the short run, the economy can be in short-run equilibrium but long-run disequilibrium. Changes in money wages and resource prices are the factor that adjusts output back toward long-run equilibrium. If short-run equilibrium is above the full-employment level, aggregate demand has grown faster than long-run aggregate supply, so the price level has increased. With money wages constant in the short run, the rising price level has reduced workers’ real wages. As a result they will increase their wage demands. As producers increase the money wages they pay (note that our focus now changes from the short run to the long run), their costs increase, and they will supply less output at each price level. This represents a decrease in short-run aggregate supply (a shift left to a new SAS curve) and a move along the aggregate demand curve, increasing the price level further and reducing output to its full-employment level.