Answer : The number of single bonds, double bonds, triple bonds, and unshared pairs of electrons on the central atom are, 3, 0, 0 and 0 respectively.
Explanation :
Lewis-dot structure : It shows the bonding between the atoms of a molecule and it also shows the unpaired electrons present in the molecule.
In the Lewis-dot structure the valance electrons are shown by 'dot'.
The given molecule is, 
As we know that boron has '3' valence electrons and chlorine has '7' valence electrons.
Therefore, the total number of valence electrons in = 3 + 3(7) = 24
According to Lewis-dot structure, there are 6 number of bonding electrons and 18 number of non-bonding electrons.
From the Lewis-dot structure we conclude that,
The number of single bonds, double bonds, triple bonds, and unshared pairs of electrons on the central atom are, 3, 0, 0 and 0 respectively.
