Elon Musk's legal team is honing in on a Twitter whistleblower and his scathing allegations, as the billionaire tries to walk away from a deal he made to buy the company. Extreme weather, from floods to drought, continues to plague regions around the world. Ukrainian President Volodymyr Zelensky warns of increased Russian military pressure this week. CNN's review of financial documents reveals that one donor is responsible for the single biggest public contribution to a political nonprofit - we'll tell you where that money is flowing. Plus, a new study suggests that electrical currents sent to the brain may improve memory.

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