Yes, it is true that in general the Northeast was the region most opposed to the annexation of Texas, since this would have meant an expansion of Southern power, which many in the Northeast wanted to avoid.
I'm pretty sure its just the 2nd answer choice
because the who point of the airlift was to send supplies to allies surrounded by communism to relieve them and keep them from "turning" to communism
hope this helped sorry if you got it wrong :)
Answer:
Europeans could not navigate African rivers, which had many rapids, cataracts, and changing flows.