Ever since your grandmother has her heart valve replaced, she has taken Coumadin daily to thin her b

Ever since your grandmother has her heart valve replaced, she has taken Coumadin daily to thin her blood to reduce her chance of blood clots and stroke. Recently, when she complained about a headache, she asked you to bring her some aspirin and water. If you know, however, that aspirin has blood-thinning properties, how would you assess the risks and benefits of giving your grandmother aspirin for her headache?
A) Likely safe and effective
B) May be safe; efficacy unclear
C) May work, but safety uncertain
D) Dangerous or ineffective