every cell has work to do but different cells may have different jobs in multicellular organisms, cell with the same type of job often work together. These group of specialized cell from tissue in turn, tissue often group together to form larger units called organs the heart is an organ; so is the stomach.
B. the intensity o stimulus and the observer's criteria.
A, B, D, and E are all wrong. C is the right answer. C is a compound.
A, B, D and E are not unique. A pure substance is something with unique characteristics and if it can be broken down, the result is two or more pure substances. AKA only compounds and elements. This is an easy question so try to study.
