Answer:
Since the middle of the 20th century, scientists <u>have found</u> cures for many diseases. However, so far no one <u>has discovered</u>
Explanation:
those are the perfect tenses for (find) and (discover)
Answer: 1. "It was idle, he knew, to get between a fool and his folly" means that it was useless and unimportant to make a fool understand something. 2. The fool is Hal. 3. His folly was his lack of good sense, trying to wake the dogs up. 4. John Thornton thought it was non-sense to intervene because regardless of the past warnings of the ice breaking down, he still wanted to wake the dogs up and continue moving.
Explanation: In the story, the team that is traveling towards their destination encounters difficulties to cross the river. John Thornton warns them that the ice is melting and that they might sink If they continue. Despite all the tragedies and losses the team has had in the trip, Hal ignores the warnings and tries to wake the dogs up. Thornton concludes that trying to convince a fool and his lack of non-sense is useless and unimportant since there is no way Hal will understand.
Based on the passage, the most accurate predection is B.