How did Darwin's 'On the Origin of Species' synthesize previous scientific ideas to present a cohesive theory of evolution?

• A. By integrating ideas of gradualism and natural selection to explain the diversity of life.
• B. By solely focusing on genetic mutations without considering environmental factors.
• C. By presenting evolution as a rapid change due to catastrophic events.
• D. By dismissing all previous scientific ideas in favor of a new religious doctrine.

Answer: (A)