The board of directors believed that Mr. Walt's remark on the current issue was highly------- given the circumstances

(a) appropriate  (B) -ly (C) -s (D)-tion

문제입니다... 여기서

The board (of directors)believed that Mr. Walt's remark (on the current issue) was (highly)------- given the circumstances

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    S                                      3V       접           S                                                          2V   부사

까지는 이해가 되서 빈칸이 주격보어(해석상 명사가 아닌 형용사)가 되어 (A)가 답이되건 알겠는데.. 뒤에 given the circumstances의 구조는 어떻게 되나요..

뒷구조가 이해가 안되서 틀렸습니다..