C = 95.9 % of the test group given placebo has not had heart attacks, while 97.3 % of people who used the medicine where heart attack free
Naturally, we would prefer alternative A that decreases the number of heart attacks by a full 33 %.
The funny thing is that it´s the same medicine and the same study. The results of the "Helsinki Heart Study" were:
4081 patients have been observed for 5 years
2051 received the real medicine. 56 of them had a heart attack
2030 received placebo. 84 of them head a heart attack.
The treatment was successful in 28 additional cases. That is 33 % of 84 heart attacks without the medicine. The placebo was ineffective in 84/2030 cases = 4,1 %. The treatment only in 56/2051 = 2,7 % of cases. That is a reduction of 1,4 %. The treatment made 2051 people attack free = 97,3 % - as opposed to the placebo with 95,9 %.