The main goal of an alchemist was to

A make gold by mixing inexpensive substances.

B further understand the world around them.

C come up with cures for diseases.

D all of the above

It's D.

Many alchemists wanted to create the sorcerers stone (creates gold according to a legend).

They studied ores to find out more about the world.

Plus, they also wanted to cure diseases with their practice. (To this day you see stone therapy, which is said to be beneficial for your health)