appreciation exhaustive presume speculate undermine 1. Canadian officials would not publicly ______ on the cause of the crash, but Trudeau called for a full international investigation. 2. Levin’s reporting is ______ — a study of welfare reform, a deep dive into FBI files and old court transcripts 记录 . 3. Upon arrival, each student was given an actual gift as a token 象征 of ______ for their participation. 4. The court must ______ innocence until there is proof of guilt. 5. In 1971, Richard Nixon freed the dollar from the gold standard 金本位制 , a decision that might have ______ the dollar’s global supremacy 优势 .