Name the best known contribution of Sir J. C. Bose.

Explanation

**Step-by-Step Text Solution:**

1. **Identify the Subject**: The question asks for the best-known contribution of Sir Jagadish Chandra Bose, who is a notable figure in the field of science.

2. **Recognize His Contributions**: Sir J. C. Bose is renowned for his work in various scientific fields, particularly in plant physiology and biophysics.

3. **Highlight the Key Invention**: One of his most significant contributions is the invention of the "crescentic galvanometer," which is a device used to measure the growth of plants.

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