The bankruptcy of which company invited the panic of 1873

Hello there!

I believe it was the Union Pacific Railroad.

I hope this is part of the options. Best of luck!

Cpopulation density

The answer is c, i, iii, and iv. this is because farming and mining deal with harvesting raw materials, construction work falls under manufacturing, and piloting a plane is a service. ii is wrong because making bread is using  raw materials to produce goods, which would fall under the secondary sector, not primary.