The construction workers _______ to construct the bridge.

The correct answer is Option B: 'left no stone unturned'. This idiom means to make every possible effort or try everything one can to achieve a goal. In the context of constructing a bridge, it implies that the workers exerted maximum effort and did not overlook any task or detail to ensure successful completion.\nOption A, 'turned over a new leaf', means to start behaving in a better way or make a fresh start, which does not fit the context of construction work. Option C, 'signed on the dotted line', refers to formally agreeing to a contract or deal, which is unrelated to the physical act of building. Option D, 'ran helter skelter', means to move in a confused or disorderly manner, which contradicts the organized effort required for such a large project. Therefore, only Option B logically completes the sentence to convey that the workers made every possible effort.