Strongest inter-molecular H-bond is present in _____
and
In options a and b, H-bonding is not possible.
In -COOH group present in option C, the electro-negative O is attached to H and C.
O will pull e- from C which has higher electro-negativity than H. So, the charge separation between O and C is low.
Since H is less electronegative than C, O will pull e-from H more.
This results in higher degree of charge separation. This will result in stronger H-bond in H2O and H2O2.