You will be given a definition of a task first, then some input of the task.
In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.

Question: Was there a treatment available for astigmatism during World War I? Passage:Achille Honore Van Acker was born into a working class family in Bruges, Belgium in 1898 as the youngest of 12 children. He only attended school until the age of 11. Despite entering the workforce, Van Acker read widely and joined several social associations in Bruges. At the outbreak of World War I, he was refused by the Belgian Army because he suffered from astigmatism. While the Germans occupied most of Belgium, Van Acker fled into the small section of unoccupied territory behind the Yser Front where he worked in various menial capacities. Mixing with Belgian soldiers during the war, Van Acker became involved in socialist politics, developing a distinctive ideology based on moderate social democracy. After the end of the war, he returned to Bruges and joined the Belgian Labour Party (Belgische Werkliedenpartij, POBBWP) and became active in socialist groups, trade unions, and cooperatives.
Links: a. World War I b. Cooperative c. Yser Front d. Working class
Output:
a