What if I say the first one as 'Once they saw the report from the medical examiner, the investigators did not doubt that the body recovered from the river was that of the man who had attempted to escape from the state prison'
i replaced had seen with saw and had not with did not.. is it correct?
In the orginal correct answer, what are past perfect verbs had seen and had no doubt doing? to which past action these two precede?
also for second question i have the similar question.