Caruana is a big specialist in the Arkhangelsk, one of the most dynamic choices for Black in the Ruy Lopez.
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1b5  3... a7a6  4. b5a4  4... g8f6  5. e1g1  5... b7b5  6. a4b3 