Explanation
Correct answer: B.
Choice B is the best answer. “As a result” logically signals that the information in this sentence about Amaya leaving Spain to perform abroad is a result of the previous information about the Spanish Civil War.
Why the other choices are wrong
Choice A
Choice A is incorrect because “in comparison” illogically signals that the information in this sentence is being compared to the previous information about the Spanish Civil War. Instead, Amaya leaving Spain is a result of that war.
Choice C
Choice C is incorrect because “first of all” illogically signals that the information in this sentence is the beginning of a sequence of events. Instead, Amaya leaving Spain is a result of the event (the outbreak of war) described in the previous sentence.
Choice D
Choice D is incorrect because “for example” illogically signals that the information in this sentence is an example supporting the previous statement about the Spanish Civil War. Instead, Amaya leaving Spain is a result of that war.