How can the design of a building, such as a concert hall, reduce unwanted noises and echoes?

Which mantle is under the crust the upper mantle or the lower mantle i think it's upper let me know if i'm right

What did not occur in the proterozoic eon a)the oxygen levels increase greatly in the atmosphere,b)the emergence of the eukarya , c)muti cella’s eukaryotic organisms began to diversify,d)anaerobic bacteria kept thriving with more oxygen

Which of the following is a true statement? question 8 options: populations can't evolve, only individual organisms. individuals have adaptations that can change over time. individuals have traits that may or may not make them successful at reproduction. individuals evolve to have adaptations.