In the Figure Shown, What Does the Dotted Line Represent

In the figure shown, what does the dotted line represent?

A) transfer of the electron from the hydrogen atom to the nitrogen atom
B) sharing of electrons between the ammonia and water molecules
C) a Van der Waals interaction
D) an electrostatic interaction between the partially- positive hydrogen and the partially- negative nitrogen
E) an interaction between a hydrophilic and a hydrophobic molecule