Understanding Chemical Evolution vs. Biological Evolution
Chemical evolution refers to the process by which simple chemical compounds gradually transformed into more complex molecules, eventually leading to the origin of life. This concept suggests that life did not appear suddenly but rather evolved from non-living chemical systems.

Key Proponents
- **Oparin and Haldane**: They are known for their work on the theory of abiogenesis, positing that life originated from simple organic compounds in a primordial environment. They suggested that the conditions on early Earth facilitated the formation of complex organic molecules, which ultimately gave rise to living organisms.
- **Pasteur and Miller**: Although Louis Pasteur is famous for disproving spontaneous generation and advocating for biogenesis, Stanley Miller is known for the Miller-Urey experiment, which simulated early Earth conditions and demonstrated the synthesis of amino acids. However, they did not propose a comprehensive theory that chemical evolution preceded biological evolution.
- **Darwin and Wallace**: They are known for the theory of natural selection and biological evolution but did not delve into the origins of life from non-living matter.
- **Darwin and de Vries**: While Darwin focused on natural selection, Hugo de Vries contributed to genetics. Neither specifically proposed the idea of chemical evolution preceding biological evolution.

Conclusion
The correct answer is **option 'A' (Oparin and Haldane)**, as they were the ones who proposed that chemical evolution occurred before biological evolution. Their theories laid the groundwork for understanding how life could emerge from non-living chemical processes, setting the stage for modern evolutionary biology.