Which sentence uses commas correctly? a. volcanoes spew molten rock and, they mostly exist along the pacific rim. b. the blue whale is the largest animal on earth and it is larger than any of the prehistoric dinosaurs. c. computers are useful tools, and, they are becoming more powerful every year. d. seaweed floats in the ocean, and some kinds can be harvested for food.

Which of these is not a criticism of the concentric zone model? it does not accurately describe cities after the rise of suburban development. it only applies to cities that grew after the development of the automobile. it assumes that inner-city areas will always be repurposed instead of abandoned. it places too much importance on the traditional central business district.