You may have selected answer (c) because you learned about the structure of water through the Valence Shell Electron Pair Repulsion (VSEPR) model.

VSEPR rather blithely assumes that all the electron pairs around an atom are free to orient in an optimal way to minimize pair-pair repulsion. VSEPR explicitely denies that the atom imposes any constraints on the pairs. But in fact it is undeniable that the singly occupied 2p orbitals in O are 90° apart. We think it is better to ask why the bond angle of water opens up from the nominal angle of 90° to something over 100° than to try to explain why it deviates from VSEPR's prediction of 109.5°.

We'll follow this up later...