[单项选择]

Formal economic forecasting is usually based on a (1) theory as to how the economy works. Some theories are complicated, and their application requires an elaborate (2) of cause and effect. Others are relatively simple, (3) most developments in the economy to one or two basic factors. Many economists, for example, believe that changes in the supply of money (4) the rate of growth of general business activity. Others (5) a central role to investment in new facilities-- housing, industrial plants, highways, and so forth. In the United States, where consumers (6) such a large share of economic activity, some economy believe that consumer decisions to (7) or save provide the principal (8) to the future course of the entire economy. Obviously the theory that a forecaster applies is of (9) importance to the forecasting process; it (10) his line of investigation, the statistics he will regard as most important, and ma
A. symptoms
B. clues
C. evidences
D. signals