What is the correct term for low levels of oxygen in a body of water?

In which case would a scientist choose to use a dissecting microscope rather than a compound microscope

The source of energy shown in the image is (renewable, non renewable, polluting) a drawback of building a dam is that (it will destroy ecosystems, it requires fossil fuels, it won’t be useful for irrigation)

Select all the correct answers. for a claim about the natural world to be considered scientific, what attributes must it have? a). it must be open to modification if new evidence doesn't completely support it. b). it must be based on scientific observations that can be repeated in a controlled setting. c). it must be applicable to future events and occurrences. d). it must be consistent with only a small portion of relevant observations or data.