Billions of years ago, how did earth come to have an oxygen-rich atmosphere?

Which of the following is an oxidation-reduction reaction? (pictured below)

Below, the levels of organization in a multicellular organism are shown from least to most complex. which level of organization can be described as several different types of tissues working together to perform a common task?

Asap brainliest will be which sentence about protists is accurate? all protists are unicellular and microscopic in nature. they have organelles, so protists are eukaryotic in nature. all protists make their own energy through photosynthesis.