In the following sentence, a part of the sentence is underlined. Below are given alternatives to the underlined part, which may improve the sentence. Choose the correct alternative. In case no improvement is needed, choose the alternative that indicates 'No improvement.'
He wasn't sure whether or not he had seen her before.
The use of the auxiliary verb 'had' suggests that the sentence is in past perfect tense. None of the given options can improve the given sentence. Therefore, the correct answer is option 4.