The correct answer is: D. No error
The sentence is grammatically correct. The word “due to” is used to introduce a clause that gives a reason for something. In this case, the reason for the travel delays is the inefficiency and lack of good management on behalf of the railways. The phrase “on behalf of” is used to indicate that someone is acting on behalf of another person or group. In this case, the railways are acting on behalf of the people who use their services.
The other options are incorrect because they contain grammatical errors. Option A is incorrect because the word “caused” is not followed by a verb. Option B is incorrect because the word “due” is not followed by a noun. Option C is incorrect because the word “on” is not followed by a noun.