yes, its 4.

But what's the explaination for that?

Polar molecules, such as water molecules, have a weak, partial negative charge at one region of the molecule (the oxygen atom in water) and a partial positive charge elsewhere (the hydrogen atoms in water).

 Thus when water molecules are close together, their positive and negative regions are attracted to the oppositely-charged regions of nearby molecules.

In order to get minimum steric strain , water forms H-bonds along the geometrical axis of it's BENT shape. Hence per molecule maximum our bonds are possible. 

I remember questions where we actually have to calculate the no of H-Bonds per mol . We are given a quantity of ice that melts and the latent heat of fusion and the actual amount of heat required to melt it , , might something else too . By calculating the energy difference and dividing by the no. of moles we can get the answer .Well ,I don't exactly remember the exact question.