问题如下：
The lagging indicator is an economic indicator that:
选项：
A.has turning points after the trend of business cycle has occurred.
B.can be used to forecast the trend of business cycle.
C.shows the tendencies where business cycle occurs.
解释：
A is correct.
Lagging economic indicator usually has turning points that are later than overall economy. Leading economic indicator usually has turning points that are prior to overall economy and some analysts use it to forecast the trend of business cycle. Coincident economic indicator has turning points that are close to overall economy.
考点：经济指标
解析：滞后的经济指标通常比整体经济的转折点的发生更加滞后。A选项正确。
领先经济指标通常具有先于整体经济的转折点，一些分析人士用它来预测商业周期的趋势。同步的经济指标与整体经济的拐点基本吻合。BC选项错误。
那滞后指标有什么作用？
