This sounds like the kind of question I would ask to follow up on an in-class activity. When I gave students a question like this I was looking for signs that were paying attention, thinking for themselves and being honest about their experience.
Your answer needs to be based on what you experienced. For example, if you had trouble getting a good look at the organism because it was swimming too fast, that would be a good thing to describe. Talk about how you worked on overcoming the difficulties. Based on my example, maybe you found that if you turned down the light source they organisms stayed in the field of view, or maybe you scanned around the slide and found a location where the organisms were gathering around a particle that they were feeding on.
Other typical examples of challenges that students have using a microscope include: seeing organisms at low power but not finding them under high power, trouble focusing at high power, only being able to focus on one part of the organism at a time, taking too much time preparing the slide and finding the organisms instead of having enough time to observe them, organism seem to die as you observe the, accidents (e.g. tripping over lamp wires, spilling water, breaking slides).
Your best answer will be based on your own experience. Was your teacher aware of any challenges you had? If so *definitely* talk about that!
Good luck.
