Parallelism - just keep that in mind.
whose is a subordinatior and to keep any ambiguity away second half of the parallel structure should also begin with subordinator like who/whoes etc.
Only D maintains this required parallelism.
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
...
whose is a subordinatior and to keep any ambiguity away second half of the parallel structure should also begin with subordinator like who/whoes etc.
Only D maintains this required parallelism.
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
...
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