The greatest single factor to spur the massive industrialization of the post-civil war years was a. electric power. b. the railroad network. c. agriculture. d. mining. e. the steel industry.

The answer is: b. the railroad network

Explanation:

The railroad boom began in 1862 when President  Abraham Lincoln signed the Pacific Railway Act.

Railroads helped  increase the size of markets for many products. It also stimulated  the economy by spending a lot of  money on steel, coal, timber, and other necessities

so, based on the research i've done. the u.s. government were always on a wild goose chase just to take down castro. he then retired his trone to his brother raul in 2008 due to some health issues. so it's obvious your answer would be:

castro had no allies from which he could receive aid.

hope this and have a fantastic day!

                                                    -wolfiewolffromsketch