C

Step 1: The line spectrum refers to discrete wavelengths of light emitted by atoms when they transition between energy levels.
Step 2: Gustav Kirchoff, along with Robert Bunsen, was instrumental in the analysis of spectra and was the first to explain the concept of spectral lines based on atomic emission. Kirchoff's work laid the foundation for understanding how elements emit light at specific wavelengths due to electronic transitions.
Therefore, the correct answer is C.