Concept:
Brahmi script is one of the most important ancient scripts of India.
Many Ashokan inscriptions were written in Brahmi script.
The decipherment of Brahmi script was a major achievement in Indian epigraphy.
Step 1: Understand the importance of Brahmi script.
Brahmi script helped historians read ancient inscriptions.
It gave important information about Emperor Ashoka, Mauryan administration, religion, and ancient Indian history.
Step 2: Identify the scholar.
James Prinsep deciphered the Brahmi script in the nineteenth century.
Because of his work, Ashokan inscriptions could be properly read and understood.
Step 3: Final conclusion.
Hence, the correct answer is:
\[
\boxed{\text{James Princep}}
\]