You observe a sample under a microscope. it is 200 µm in diameter and has no nucleus. what would it most likely be?

The sample would most likely be A PROKARYOTIC CELL.

Explanation:

There are different types of microscopes, which can be used to observed minute samples such as cells. Cells are of two types, prokaryotic and eukaryotic cells.

The prokaryotic cells are smaller in size compare to eukaryotic cells and they do not have nucleus. They also do not have any membrane bound organelle.

Since the sample that is bee observed under the microscope is only about 200 micrometer in diameter and has no nucleus, it is most likely to be a prokaryotic cell. A good example of a prokaryotic cell is bacteria.  

i thinking chemical change

condensation. good luck!