The farmers _____ their farms, if they had known that a thunderstorm was approaching. a. will leave. b. would leave. c. will have left. d. would have left. I need answer. Explain please?

I would choose option D: Would have left. I choose this option because the sentence is spoken in the past tense, as is option D. The other options are either present tense or future tense. Good luck to you.