Robert Koch and His Colleagues fiRst Used Agar in Bacteriological

Robert Koch and his colleagues first used agar in bacteriological media. Why was this ingredient an improvement on previous materials used to culture bacteria?

A) Agar was less expensive than the nutrients that Koch was previously using in the lab.
B) Agar can convert from liquid to solid form, and back again, very easily.
C) Bacteria growing on the solidified medium did not degrade or break down the agar.
D) Agar is a complete source of nutrients for most bacteria.