The correct option is D No sooner was the house built than the tree fell over it.
If the second event occurs immediately after the first, no sooner...than is used to express such situations. In such a structure, no sooner introduces the event that occurred first. No sooner is followed with the past tense. Options B and C are wrong since 'then' is used instead of 'than'. Thus, option D is correct as no sooner is followed by 'was'.