Writing: need an explanation

awelex
Mon, 28 May 2007 06:48:48 +0000

The following question is from the Identifying Sentence Errors part:

The first signs in six months of a pickup in consumer spending **are emerging/b, **which reduces/b the chances **that/b the Federal Reserve will lower interest rates when **it meets/b next month.

The solution says that the error is at B and that the correct sentence should read “…are emerging, reducing the chances that…”. Could someone explain that to me? I’m not a native speaker, but the original sentence sounds right to me…