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Question 149·Medium·Transitions

In the early 2000s, astronomers discovered that many stars host “hot Jupiters”—giant planets orbiting extremely close to their suns, a finding that challenged prevailing models of planet formation. _____ computer simulations have been refined to account for planetary migration, showing how such massive bodies can drift inward after forming in distant, colder regions of the protoplanetary disk.

Which choice completes the text with the most logical transition?