Three segments of the following sentence have been underlined and given as options. One of them may contain an error. Select the option that contains the error. If you don’t find any error, mark ‘No error’ as your answer.
Since his son has not yet completed the age of eighteen, he was reluctant to fulfil his son’s demand of getting a motorbike.

The correct answer is he was reluctant.

Explanation:
The given sentence is: "Since his son has not yet completed the age of eighteen, he was reluctant to fulfil his son’s demand of getting a motorbike."

In this sentence, there is a grammatical error regarding verb tense consistency between the dependent clause and the main clause.

1. The dependent clause "Since his son has not yet completed the age of eighteen" uses the present perfect tense (has not yet completed), which indicates a condition that applies in the present.
2. The main clause "he was reluctant..." uses the simple past tense auxiliary verb (was), creating a tense conflict with the present situation described in the dependent clause.
3. To maintain proper sequence of tenses, the verb in the main clause should also reflect the present time frame by using "is" instead of "was" (making it "he is reluctant...").

Therefore, the segment containing the error is "he was reluctant".