1. In mixed economy both the state and the private sector play (pres simp - to play) an important role.
2. He wrote (past simp - to write) this book in response to the Great Depression of the 1930s.
3. Keynes was (past simp - to be) a British economist.
4. Keynes's work aroused (past simp - to arouse) Frank P. Ramsey to outline his own "subjective" theory of probability.
5. Keynesian economics is (pres simp - to be) the opposite of laissez-faire economics.