Concept:This is a third conditional sentence, which requires the past perfect tense in the "if" clause to express an unreal past condition.
Explanation:The sentence describes a hypothetical past situation where paying dues on time would have prevented penalties and protected the credit score.
The standard structure for such unreal past conditions is: If + past perfect, would/could have + past participle.
The original phrase "paid" is in the simple past tense, which does not correctly fit this conditional structure.
So, it must be replaced with "had paid his dues on time", which uses the correct past perfect form.
Option A uses the future tense, which is unsuitable for a past hypothetical context.
Option B uses the simple present tense, which does not match the past conditional frame.
Option D uses the present perfect tense, which is also inappropriate here.
Option E is incorrect because the original sentence is not grammatically correct and does require correction.
Answer:Option C: "had paid his dues on time"
Correct sentence: If the customer had paid his dues on time every month instead of delaying payments repeatedly, the bank would not have imposed additional penalties, and his credit score could have remained unaffected.