Which of these changes during the industrial revolution led to greater efficiency?
a)workers received labor rights.
b)major labor unions were formed.
c)slavery and other forms of forced labor were eliminated.
d)animal & human power were generally replaced with steam power.

D) Animal & human power were generally replaced with steam power.

The league of nations was found in 1919 to keep peace after world war l.but it failed to prevent world war ll in 1939,so in 1945 the nations of the world set up a new organization,the united state (un).since then, the un has encouraged international cooperation and worked to resolve conflict