How did nationalism increase tension among european countries

Because since they all had so much pride in their own countries it would cause tension because they all think they are the best and they would compete for territories.

Explanation:

explanation:

there are two statements that are incorrect.

1. the marshall plan was a lend lease program. it was an economic plan that europe redevelop itself after wwii.

2. einstein didn't really do anything to further the allied cause in building the bomb. he merely sent a letter to fdr telling him (in 1939) that if the united states entered the war, perhaps it would be wise to build the bomb before germany did. i would say this answer is incorrect, but when america entered the war 2 years later, fdr thought it might be a good idea to take einstein's advice.

the 4th choice is definitely so wrong that is likely the single answer of this question

answer; people where able to travel across the u.s.a faster than any other mode of transportation,travel time was about a week,from coast to coast