Answer:
The correct answer is option 'B' - Went.

Isolation of Auxins
Auxins are plant hormones that play a crucial role in various processes such as cell elongation, apical dominance, root formation, and fruit development. In the early 20th century, scientists began to investigate the nature and properties of auxins, leading to the isolation of these plant hormones.

Went and the Isolation of Auxins
Frederick Charles Went, a Dutch-American botanist, was the scientist who isolated auxins from the tips of coleoptiles of oat seedlings. Went conducted his research in the 1920s and 1930s and made significant contributions to the understanding of plant hormones.

Experiment by Went
Went conducted an experiment using oat seedlings to isolate auxins. He observed that when the tips of coleoptiles were removed, the growth of the seedlings was inhibited. However, when these tips were replaced or placed near the cut area, the growth resumed. This observation led him to hypothesize that the coleoptile tips contained a substance responsible for promoting growth.

Methodology of Went
To isolate this growth-promoting substance, Went developed a method. He extracted the coleoptile tips using ethanol and then purified the extract to obtain a crystalline powder. This powder, known as auxin, was found to promote growth when applied to coleoptiles.

Contribution to the Understanding of Auxins
Went's isolation of auxins from oat coleoptiles was a significant breakthrough in the field of plant physiology. It provided evidence for the existence of a substance that regulates plant growth and development. His research paved the way for further investigations into the functions and mechanisms of auxins in plants.

Conclusion
In conclusion, the scientist who isolated auxins from the tips of coleoptiles of oat seedlings was Frederick Charles Went. His research and discoveries greatly contributed to our understanding of plant hormones and their role in plant growth and development.