Answer 1: D. had left - having collaborated Explanation: The correct answer is "had left - having collaborated". The first blank requires a past perfect tense because it refers to an action completed before another past action (the accusations). The second blank requires a gerund (-ing form) after the preposition "of". Answer 2: B. was to have been presented Explanation: The correct answer is "was to have been presented". This structure is used to talk about plans or expectations that were in place in the past, but which did not happen. In this context, the skull was expected to be presented at the conference, but it was not due to the coronavirus outbreak.