What changed about the river valley civilizations as they rose and fell ? a. the environment b. the actual water formations c. the religion

hello,

the steamboat is your answer.

it seems like its the only form of transportation on the choices.

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