Option (D) is correct because the provided text explicitly states that Louis Pasteur postulated the germ theory of disease. The context mentions that based on his experiments, Pasteur disproved the theory of spontaneous generation and postulated the germ theory, which states that microorganisms are the cause of infectious diseases. In contrast, the text describes Robert Koch as the one who 'further proved' the germ theory through his experiments with Bacilli and anthrax.