c. like a slide
Autochrome is an additive color 'screen-plate' process: the medium contains a glass plate, overlaying random mosaic of microscopic grains of potato starch, with lampblack filling the space between grains, and an impermeable black-and-white, panchromatic silver halide emulsion. The grains are a mixture of those dyed orange, green and violet, which act as color filters. The plate is processed as a slide — that is, the plate is first developed to a negative image and then reversed to a positive image — and the starch grains remain in alignment with the emulsion after processing in order to allow the colors to be seen properly.
note that the answer would not be (a) because colloidon is involved in the ambrotype process which is different from autochrome.
it wouldn't be (b) negative because the final image in autochrome has colors but has a "dream-like", impressionist quality (hazy effect).
it is definitely not (d) black and white.
so, for me the best answer is (c).
goodluck.
