Understanding the argument -
Magnetic resonance Imaging(MRI)-a noninvasive diagnostic procedure can be used to identify blockages in the coronary arteries. - Fact
In contrast to angiograms-the invasive procedure customarily used -MRI's pose no risk to patients. - Fact
Thus to guarantee patient safety, in the attempt to diagnose arterial blockages ,MRI's should replace angiograms in all attempts at diagnosing coronary blockages. - Conclusion
Option Elimination -
A. Angiograms can be used to diagnose conditions other than blockages in arteries - Weakener.
B. MRI's were designed primarily in order to diagnose blockages in the coronary arteries - But "angiograms" could still be better? Isnt it? At best, it is out of scope. Our scope is limited to strengthening the conclusion, which is "MRIs should replace angiograms."
C. Angiograms reveal more information about the nature of blockage than a MRI can - Weakener
D. An MRI is just as likely as an angiogram to identify an arterial blockage - ok. On top of that, it has the positives given in the argument.
E. Some patients for whom an angiogram presents no risk are unwilling to undergo an MRI - "willingness" is out of the scope of this argument. Our scope is limited to strengthening the conclusion, which is "MRIs should replace angiograms."