Answer:
c. Phase 3
Explanation:
The Phase 3 of a clinical trial involves around 1000-3,000 subjects with the diagnosis(signs and symptoms) which the new medication is meant to cure.
Such clinical trials in this phase may last for years.
It's main purpose is to determine the new medication effectiveness and efficiency in relation to old medication for the same the diagnosis(signs and symptoms).
In this case, the safety and effectiveness of a new medication treatment is evaluated on the largest number and class of participants.
