The past perfect verb tense is used to
talk about actions that were completed before some point in the past. The past
perfect tense is written as had + [past participle] irrespective of
the subject being singular or plural. In the given context, option A is the
correct answer as I + had + seen (past participle of the verb ‘see’) follows the correct pattern of verb agreement in a sentence where both the verbs (asked as well as seen) are in accord.
‘Had I seen’ is incorrect as the past participle should directly follow the
verb.
In case of has/have + [past participle] form the tense is present perfect.
However, the context refers to asked (V1) and thus, past perfect tense should
be used for the following verb also.
“If did I see her’ is grammatically incorrect.