Which of the following choices best explains what Dumas, Bouley, Paul Bert and Voulpian have in common (paragraph 2)? (Alas! mine is the bitter grief that I enter it, a man "vanquished by time," deprived of my masters, even of my companions in the struggle Bouley, Paul Bert, and lastly Vulpian, who, after having been with you, my dear Grancher, my counselor at the very first, became the mo energetic, the most convinced champion of this method. )
A. They did not believe in the scientific method Pasteur is describing.
B. They fought in battle for France.
C. They are all Pasteur's students.
D. They are all dead.