The most common types of sleep disorders are insomnia, sleep apnea, narcolepsy and sleepwalking" is an example of a

The most common types of sleep disorders are insomnia, sleep apnea, narcolepsy and sleepwalking" is an example of a central idea. The term central idea is a one-sentence statement that sums up or encapsulates the major ideas of a speech. It describes the main thought or principal theme and it  is the main point that the author is making.

North America, Europe, and Africa.

The triangular trade is called that because the path forms a triangle in the North Atlantic Ocean.

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