The correct option is A Metaborate
Metaborate is formed in borax bead test.
On heating, borax loses water of crystallisation and swells up to form fluffy mass. On further heating, it melts to give a clear liquid which solidifies to a transparent glassy bead consisting of sodium metaborate and boric anhydride.
Na2B4O7⋅10H2O△→Na2B4O7+10H2O740oC⟶2NaBO2Sodium Metaborate+B2O3
CuO+B2O3→Cu(BO2)2 blue bead
Thus, Metaborate is formed.