An unknown compound (A) has a molecular formula `C_(4)H_(6)`. When (A) is treated with excess of `Br_(2)` a new substance (B) with formula `C_(4)H_(6)Br_(4)`. Is formed (A) forms a white ppt. with ammonical silver nitrate solution. (A) may be,
A. Butyne-1
B. Butyne-2
C. Butene-2
D. Butene-1