A boy who possesses Rp1.000,00 is confronted with two choices either to buy a piece of cake or salted egg. The price of the cake equals with a salted egg. If the determines to buy the cake, he can’t buy the egg and on other way round.

The act of making decision in economics is known as...

A. the principle of opportunity cost

B. the cost of doctrin alternative

C. the law of scarcity

D. the law of diminishing return

E. the principle of economic