Which of the following is one of the five causes of a business cycle?
a. decrease in consumer demand
c. recession
b. external shocks
d. none of the above

C recession is one of the five causes of a business cycle. 
Business cycles are measured by looking at the growth rate of the gross domestic product of a country. There are five causes of a business cycle:
1. Changes in interest rates2. Changes in house prices3. Changes in consumer and business confidence 4. The local or world economy moves into a recession5. The local or world economy moves out of a recession. 
These causes can also be seen as unstable fluctuations rather than stable cycles. 

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answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms