The following image is of a diatom. It lives in water and gets food from photosynthesis. It is encased in a hard shell made of something similar to glass or sand. Image by Damián H. Zanette A diatom is a(n) _______ because it has _______.
A. singled-celled organism; only one cell
B. multi-celled organism; specialized parts
C. vertebrate; a skeleton
D. insect; an exoskeleton