You will come (a)/ to my party tomorrow (b)/ isn’t it ? ©/ No error (d)

Answer

3

Explanation

Structure of Question Tag in Future Tense with will is as follows:
`{:("You will come to my party tomorrow."),(""darr " "darr ),("Sub. Aux. V"),("won.t " " you ?"),(darr" " darr),("Aux. V + Not Sub."):}`
Contraction of wil not is won.t .
Hence won.t you is the right usage.