Which revises the sentence to create a new, complex sentence?

Based on the scientists’ recommendations, the new safety requirements were enacted, and fewer accidents occurred.
Many accidents occurred, so based on the scientists’ recommendations, the new safety requirements were enacted
Based on the scientists’ recommendations, the new safety requirements were enacted so that the number of accidents diminished.
People were concerned by the number of accidents, so based on the scientists’ recommendations, the new safety requirements were enacted.