Approximately what percentage of the world's extinct species became extinct before humans appeared on earth?

If there is a permanent decrease in demand in a perfectly competitive market, then there is an initial ________ in price and existing firms ________

A) rise; make an economic profit B) rise; incur an economic loss C) fall; make an economic profit D) fall; incur an economic loss

What is the most compelling evidence for the Keynesian interpretation of the Great Depression?

a. Increases in both the interest rate and the quantity of money b. Decreases in both the interest rate and the quantity of money c. An increase in the interest rate and a decrease in the quantity of money d. A decrease in the interest rate and an increase in the quantity of money