The correct option is A Will you be in London next week?
When we change an assertive sentence to an interrogative, we change its form (from affirmative to negative or from negative to affirmative).
We change a positive sentence to a negative sentence.
In the same way, we change a negative sentence to a positive interrogative.
The given sentence is in negative: 'won't be', which is a contraction of 'will not be'. Hence its question form is in the positive: 'will... be'.
Option D: This interrogative is in the affirmative, 'Will you be in London...?'
Hence option D is correct.
Option A: This question is in the negative. As explained, while changing the assertive sentence to interrogative, we must change it from negative to positive.
Option B: The tense of the verb 'will be' has changed to present perfect 'Haven't you'. Also, it's the negative form, and this verb contradicts with the time when the action will take place: next week.
Option C: Similarly, 'hadn't you' refers to the past perfect tense, whereas the sentence is in the future. (Also, it does not go with the present verb 'be': hadn't you be.)
Hence options A, B and C are incorrect.