The correct option is B She asked when I would be graduating.
Direct speech is a sentence in which the actual words of the speaker are quoted.
Indirect speech is a sentence in where we report what someone said, without quoting his exact words.
In Future Continuous Tense 'will be' changes into 'would be'.
Here, option B is correct. 'Will be' changes into 'would be'. Pronoun 'you' changes into 'I'. It can be changed into 'he' because listener( the person to whom speech is reported) is absent.
In option A sentence formation is wrong as verb comes after noun/pronoun. So, it is incorrect.
In option C tense is not changed. So, it is incorrect.
In option D verb is wrong. So, it is incorrect.