Parts of the following sentence have been given as options. One of them may contain an error. Select the part that contains the error from the given options. If you don’t find any error, mark ‘No error’ as your answer.
How foolish I was to have believe that young woman!

Correct option is A

Option (a) contains an error.
Detailed explanation of error: After to have, we require the past participle (V3) to form the perfect infinitive.
So, to have believe ✗ should be to have believed ✓.
The perfect infinitive is appropriate because the believing happened before the time of realisation ( I was).
Corrected sentence: How foolish I was to have believed that young woman! (You could also use the simple infinitive to believe for a general comment, but the exam tests V3 after “to have”.)
Grammatical rule used: Perfect infinitive = to have + V3, showing an action earlier than the time expressed by the main verb.
Example: She was lucky to have escaped the fire.
Information booster: We often use the perfect infinitive after evaluative adjectives ( foolish, wise, fortunate, careless) to show the earlier action: It was careless to have left the door open.