So here's a question i need answered:

you view a sample under a microscope. how can you determine if the sample is living?

The most probable answer to this question would be to look for cell membranes.

You can identify them by the usual and the common look of cells described in every science book. living organisms or sample that are living and were once living, all have cell membranes to show when glanced over the microscope. The best microscope to utilize would be the electron microscope. This would allow you to determine if the living sample is still living or was living through observing its mitochondrion if it is still in activity.

Or if it has moving cells or whatever their called