The sentence which describes a cause-and-effect structure is the following: "Working on a wind turbine can involve hazards, such as falls, fires, or fatigue." (D).
A sentence containing a cause-and-effect structure means that you should have, in 1 sentence:
Here, the fact that people are working on wind turbines is the cause, because it leads to possible consequences: they can fall, trigger fires, or become fatigued (these are the effects).