I would say all of the above
Is that an option?
Answer: The oxygen content at the source of the streams or rivers is higher as compared to the mouth of the river. Consequently, the organisms which require more oxygen tend to find at the source of the rivers whereas the organisms which require less oxygen tend to find at the mouth of the river.
Explanation:
Answer:
a mineral is scraped or rubbed hardly on sandpaper or unglazed porcelain
( please mark me as brainliest that would be most appreiciated )