The correct option is B she had got only 80 out of hundred
When a sentence is changed from direct to indirect speech, the subject pronoun, verbs and tense forms also change. (This is because the speech is reported by someone else, and the tense of the direct speech goes one tense back as it's spoken at a later time now.) The meaning of the sentence should not be changed.
The direct speech "I have got only..." is in the present perfect tense. Hence while being reported, it changes to its past tense equivalent, i.e., past perfect tense.
Option B: This is the complete reported speech of the given direct speech. The subject pronoun 'I' has changed to 'she', the present perfect verb 'have' changes to past perfect 'had'. Hence B is correct.
Option A is incorrect because it does not state a sentence, the subject and verb have been eliminated.
Option C is incorrect because the auxiliary verb 'had' is missing. This verb is essential to indicate the past perfect tense.
Option D is incorrect because the modal verb 'would' is an extra, which isn't provided or implied in the direct speech. Also, 'would' is the past tense of 'will' in reported speech. It refers to a future action, whereas the action here 'have got' has just taken place.