Why is it difficult to explain the causes of business cycle?

What is scarcity and why does scarcity always exist? A trough in the business cycle occurs when.......? Explain the different types of economic activities? What were some of the pros and cons of using wampum and barter in an economic system? What kind of goods require search costs? How much is a 20 dollar 1980-1982 worth? What is the supply and demand for banquet hall? If a test of hypothesis has a type 1 error probability 01? What are the three major components of investment spending and how are they related to the interest rate? 3 main theories of a producers duties to the consumers? What is the difference between a consumer good and a capital good? Suppose nominal GDP in 2006 was 100 billion and in 2007 it was 260 billion The general price index in 2006 was 100 and in 2007 it was 180 Between 2006 and 2007 the real GDP rose by approximately? What areas are affected by OPEC? What are the examples of international resources or resources that lie beyond the Exclusive Economic Zone? Inter-specific competition is competition among what? What is the average price of land per acre in the state of tn.? Why does the game of economics do not have no winner? The price paid for the use of money is? Which statements best explains how using a production possibilities frontier helps set up efficient production? In a free market supply and demand determines?