Anna is observing slides of unlabeled organisms. The organisms are unicellular, have delicate glass-like cell walls with sculpturing, and show all the cell organelles, including chloroplasts. Which organism is she observing?

The answer is diatoms.

The organism is unicellular, but contains cell organelles, so it must be in the domain Eukaryota. It also has chloroplast, so it could be some plant or algae, but since it is unicellular it must be algae. Among the algae, diatoms are specific for their glass-like cell walls with sculpturing.