The correct sentence is b) If you warm water, it will boil.
Option a) is incorrect because it uses an incorrect verb tense. The correct sentence would be: "If I had time, I would have written this book that I wanted."
Option c) is incorrect because it uses a double conditional "if...would have." The correct sentence would be: "I would have bought a house if I had had enough money."
Option d) is incorrect because it uses a future tense to describe a future event. The correct sentence would be: "When we move to another city, our new life will begin there."