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Help the clumsy time traveler complete his diary entry about accidentally changing history.
Looking back, I realize I ____________________________________________ a neon tracksuit during my undercover mission to the Renaissance. Furthermore, Leonardo da Vinci _________________________________________ to paint his masterpiece if I hadn't spilled my futuristic, glowing sports drink all over his blank canvas.
...I ought not to have been wearing a neon tracksuit... Leonardo da Vinci might never have been inspired...
ought not to have been wearing: To express regret about an ongoing past action using "ought," the correct negative form is ought not to have been + -ing. Placing "not" after "to" (ought to not...) is grammatically incorrect.
might never have been inspired: This uses a past modal in the passive voice (might have been + past participle) to describe a hypothetical possibility in the past, matching the third conditional "if" clause that follows it.