John was very much in love with Mary, so John told Mary, "Will you marry me?"
The two ways of relating what a person has said are 1)direct and 2)indirect (reported).
In the direct speech, the exact words of the original speaker are repeated.
In the indirect speech (reported speech), the exact meaning of what the speaker told is expressed but not necessarily in the speaker’s exact words.
Option A is correct as the appropriate introductory verb 'asked' is used, appropriate conjunction 'if/whether' is used and the given question is in future tense so the reported sentence uses the conditional 'would' and 'you' and 'me' becomes 'she' and 'him' respectively, and it ends with a full stop.
Options B, Cand D are not correct as 'told' can't be used, 'me' cannot come as it is, and 'you' is not transformed respectively.
The correct answer is A) John asked Mary if she would marry him..