If you were looking at. Multi-cellular organism with a microscope, would you be looking at a prokaryotic o eukaryotic organism. How do you know ?

Prokaryotic cells DO NOT have a nucleus, so look for those The DNA in the Prokaryotic cells is not enclosed within the Nuclear membrane. 

Mult-cellular organisms are eukaryotic organisms. When looking at a eukaryotic organism under a microscope, the cells will contain nuclei. A prokaryotic organism has no nucleus.