Answer
The bonds will be :
a. pure covalent
b. polar covalent
c. pure covalent
d. ionic bond
Work Step by Step
a. The bond is formed by sharing of electrons between the two $Br$ atoms, so it is covalent. There is no electronegativity difference, so the bond is pure covalent.
b. The bond is formed by sharing of electrons between the $C$ and $Cl$ atoms, so it is covalent. There is electronegativity difference between the two atoms (Cl is more electronegative), so the bond is polar covalent.
c. The bond is formed by sharing of electrons between the $C$ and $S$ atoms, so it is covalent. There is negligible electronegativity difference between the two atoms, so the bond is pure covalent.
d. The bond is formed between the $O^{2-}$ and $Sr^+$ ions, so it is ionic.
