Civil engineer Lorenzo Raspallo ------- as the guest speaker at the fifth annual Bridge Conservation Colloquium next month.(A) to confirm(B) to be confirmed(C) has been confirmed(D) having been confirmed정답 C를 제외한 나머지가 왜 오답인지 알고싶어요.
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A: to부정사 -> 동사불가
B: to부정사 수동태 -> 동사불가
D: 분사형 수동태 -> 동사불가