Select the largest, most inclusive biological level from the following choices.
a. cell
b. tissue
c. organ
d. molecule

The Organ is the largest biological level.

First there is a cell, and a bunch of cells make up tissues, and a bunch of tissues makes up an organ, which makes up a organ system (like the digestive system), which makes up a organism.

Molecule is more of a chemistry thing, so it's not included in Biology, the smallest unit of life is a cell.