I think the its plow i could be wrong but thats what i got
The European balance of power broke down was an effect following German unification is correct answer due to fact that Germany (except Austria) was united by militarist state of Prussia with powerful army which definitely change balance on the European scene especially that formal unification took place just after end of Franco-Prussian war which humiliated France.
B; is the answer cause it’s an opinion of Abraham Lincoln
They were fearful of the power of the British government. They did not want someone to gain too much power over them once again.