Complete the journalist's article about a very confused time traveler by choosing the correct phrase for each gap.

The eccentric scientist explained that he had been trying to visit the dinosaurs when his engine failed, and muttered that he had to fix the machine before Tuesday.

The eccentric scientist explained that he had been trying to visit the dinosaurs when his engine failed, and muttered that he had to fix the machine before Tuesday.

"I was trying" (Past Continuous) backshifts to "had been trying" (Past Perfect Continuous) when reported in the past ("explained").

When "must" is used to express obligation ("I must fix it"), it changes to "had to" in reported speech. "Must have fixed" is incorrect because it expresses a past deduction (e.g., "someone must have fixed it"), not an obligation.