In what way did alchemists contribute to the development of modern chemistry?
a. explained changes to matter in mystical, philosophical, or religious terms
b. created models of the internal structure of atoms
c. used experiments to analyze the relationship between gas pressure and volume
d. developed practical equipment, new procedures, and methods of identifying unknown substances

The correct answer is d. developed practical equipment, new procedures, and methods of identifying unknown substances

Although they were interested in mysticism, there was no place for it in science and they did not explain it in such manners. They also did not create models and didn't deal with gas pressure and volume. They mostly tried to change chemical properties of one chemical into another.

Because a model would make the investigation easier to understand