In option b,” by” is used correctly to indicate the agent of the action (”by a leading publisher”), and in option d,” by” correctly refers to the means of resolving the problem (”by appointing”).
Among scientists, the discovery of the double helix structure of DNA and the genetic code it incorporates is widely regarded to be one of the most significant scientific discovery of the twentieth century.
Thank goodness, the damage to the car was \(\underline{neglectful.}\)