The steady progress of industry in the united states was possible because:

a new sources of energy allowed industry to develop
b people developed methods to increase production
c methods of transportation and communication were improved
d all of the above

i think it would be c.

hope i'm correct

explanation:

an unexpected salary cut

frederick william of brandenburg-prussia trained his son, frederick, to be a hardy soldier. but frederick disliked rifle shooting and horseback riding. unlike his father, he was interested in french literature. he enjoyed poetry and music and, like some others of the enlightenment, he scoffed at religion. his father thought him soft, frivolous and unmindful of his duties. and when frederick refused to put his signature on a right to succession, for a few moments his father strangled him.