Is a scientific theory a guess or a proposal?

Which to produce involved from a symbiotic relationship of organisms which resulted in eukaryotic organisms contain chloroplast

Which statement best explains why cells were observed in more detail using a compound microscope than a simple microscope? a compound microscope has greater magnification ability than a simple microscope. the compound microscope was invented before the simple microscope. a compound microscope is much easier to manufacture than a simple microscope. compound microscopes were more common than simple microscopes.

What statement about energy is true