Was slavery either a as a moral issue or an economi reality the single most important cause of sectional conflict ?

Scholars have debted this question since the civil war ended. They to this day remain divided on this question. To answer it we must ask ourselves a question. If there was no slavery in the US at the time of the civil war would southern states have ceded from the union? The answer is weighted heavily to no. So the answer to this question is yes. Even though there were many other issues between the north and the south slavery was the issue that caused the southern states to leave the union.

the correct answer is:   the domino theory states that if one country in a region came under the influence of communism, then the surrounding countries would follow in a domino effect.