What causes the aurora borealis or northern lights to occur

When the solar wind gets past the magnetic field and travels towards the Earth, it runs into the atmosphere. ... As the protons and electrons from the solar wind hit the particles in the Earth's atmosphere, they release energy – and this is what causes the northern lights.

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain

that would be the steamboat because none of the other things are forms of transportation