For many years a mainstay of the economy in Seattle, Washington was commercial fishing. Many people not employed in the fishing industry were employed providing goods and services to fishermen. This is an example of

For many years a mainstay of the economy in Seattle, Washington was commercial fishing. Many people not employed in the fishing industry were employed providing goods and services to fishermen. This is an example of basic employment generating non-basic employment.  Basic employment is the job that provides goods and services to the community, however the non basic employment has the job of providing support and services to the basic employment.

the answer is crop rotation

answer; i believe the correct answer is (a) nigeria is the largest african crude (oil) supplier; /// so revenue from petroleum;