Borax is actually made of two tetrahedra and two triangular units joined together and should be written as: Na2[B4O5(OH)4]·8H2O

 The correct statement/s about borax is/are:

a.  Each boron atom has four B-O bonds    

b.  Each boron atom has three B-O bonds

c. Two boron atoms have four B-O bonds while other two have three B-O bonds

d. Each boron atom has one -OH groups