High frequency sound waves have a and higher than low-frequency sound waves

THe first fill in the blank is wavelength and the second one is pitch. So, High frequency sound waves have a shorter wavelength and higher pitch than low-frequency sound waves. Hope this helps!

these civilizations were located around fertile rivers, where they could produce an abundance of crops

its main object was the establishment of "settlement houses" in poor urban areas, in which volunteer middle-class "settlement workers" would live, hoping to share knowledge and culture with, and alleviate the poverty of, their low-income neighbors.