Explain how a swallow hole is formed

Why did large numbers of african migrate to the americas

Seed plants that lived during the carboniferous impact life on earth today because a. they are the ancestors of all plant life on earth. b. their remains formed coal, which is an important resource. c. they produced fossils that are used to date many geologic events. d. their presence caused oxygen levels to drop, allowing animals to evolve.

Most countries in the middle east must import a majority of their a. gasoline b. oil c. food d. water