What would be a best explanation for the gas accumulated in one of the inverted test tubes?

After getting the slide and microscope ready, stella is eager to see the microscopic pond water specimen! she crouches around her microscope and aligns her eye with the microscope’s eyepiece. but she's only able to see a bright white light. at this point, no specimens or cells are visible on stella's pond water slide. after taking a moment to collect her thoughts, stella realizes she can't see any lifeforms because .

Surrounded by microtubules, located near the nucleus. (don't try to google it) (give answer only if u know)

What occurs to the cell during mitosis