Which famous economist believed that if governments spend during a depression, they can revive a national economy?
a. adam smith
b. jules dupuit
c. karl marx
d. john maynard keynes

This would be John Maynard Keynes !

He was deeply skeptical of austerity measures during recession and during the Great Depression (in 1930s). He argued that during this time budget deficits were not a problem and instead they can help overcome the problems.