GMAT Sentence Correction (SC) | The study involved 1000 patients whose cardiac disease

The study involved 1000 patients whose cardiac disease was not well controlled by existing medications – drugs such as ACE inhibitors and beta-blockers –and had suffered persistent symptoms that had been lasting for at least a year.

A) and had suffered persistent symptoms that had been lasting for at least a year
B) and suffered from persistent symptoms that had lasted for at least a year
C) but were suffering from persistent symptoms that had been lasting for a year or more
D) and who suffered
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