美国二季度GDP增速2.1%好于预期，但企业投资三年来首次下滑，房地产也持续衰退。请看本报昨日的报道：

U.S. economic growth slowed less than expected in the second quarter of the year as a surge in consumer spending blunted some of the drag from declining exports and a smaller inventory build, which could further allay concerns about the economy’s health.

But the fairly upbeat report from the U.S. Commerce Department on Friday had some red flags for the 10-year-old economic expansion, the longest on record. Business investment contracted for the first time in more than three years and housing declined for a sixth straight quarter.

报道中的red flag就是“预警信号”，例如：

He’d been coughing for months before being diagnosed with lung cancer. He unfortunately overlooked the red flags.

被确诊肺癌之前他已经咳嗽了很久。不幸的是他忽略了这个预警信号。