GMAT Critical Reasoning (CR) | A new medication for migraine seems effective

A new medication for migraine seems effective, but
there is concern that the medication might
exacerbate heart disease. If patients with heart
disease take the medication under careful medical
supervision, however, harmful side effects can
definitely be averted. The concern about those side
effects is thus unfounded.

The argument depends on which one of the
following assumptions?

(A) The new medication actually is effective when
taken by patients with heart disease.
(B) No migraine sufferers
...

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