Problem 1: an invention by carl siemens make the second industrial revolution possible. what was it?

a. an expanded system of telephones

b. insulation for telegraph wires

c. a way to make large quantities of steel in a gas furnace

d. medication from coal tar

problem 2: which of the following became common in middle-class homes during the second industrial revolution?

a. televisions

b. electric lamps

c. stereos

d. electric typewriters