QUESTION $5$

In every economic model, we have variables we seek to explain or predict $($endogenous variables$),$ and a set of variables we call shift variables. Which of the following is a correct statement about these two types of variables:

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$$ a$.$ both shift variables and endogenous variables are on the axis of our graphs

b$.$ shift variables aren't on the axis of our graphs, but endogenous variables are on each graph's axis

c$.$ shift variables are on each graph's axis, but endogenous variables aren't on the axis of our graphs

d$.$ when the endogeno $s$ variables change, those changes cause changes in the shift variables on our graphs