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LFgtGrammar Nazis English sentences help needed

I need someone to dumbify how to figure out whether the sentence is a compound sentence, complex sentence, or a compound-complex sentence. And/Or to gimme answers..

1)Tornadoes, which are sometimes called twisters, can cause great destruction.

2)However, some tornadoes can last several hours; during that time they can travel two hundred miles or more.

3)Since many hit in remote areas, the exact number of tornadoes in a given year can never be known.

4)Although scientists have studied tornadoes for years, the conditions that cause these storms to develop are not fully understood.

5)First, storm clouds form a narrow line, called a squall line, which creates violent weather.

6)This violent weather produces a mass of warm, humid air that rises quickly, and more warm air rushes in to replace it.

7)Sometimes the air that is rushing in begins to rotate, and a tornado is formed

8)The mass begins to twist, and then it forms a funnel cloud that gradually extends toward the earth

9)Rain and hail start to fall, and lightning begins flashing.

10)As the funnel cloud reaches downward, it produces a hissing sound.