Why are valves present in veins but not in arteries?

Plz quick a natural resource that is replaceable through a cycle in nature or sustainable practice is called a? the subject is science

There are multiple lines of evidence that provide support for common ancestry and evolution. write 3-4 paragraphs describing at least three of them in detail. provide at least one example for each line of evidence.

When the oxygen produced by photosynthetic plants in the water dissolves in the water, which of these is being formed?