Why does water have an unusually low vapor pressure for a liquid? a.)hydrogen bonding repels water molecules at the surface, increasing the rate of evaporation. b)the oxygen-hydrogen bond in a water molecule is unusually strong, which decreases the rate of evaporation. c)the oxygen-hydrogen bond in a water molecule is unusually weak, which increases the rate of evaporation. d)hydrogen bonding attracts water molecules to one another and slows the rate of evaporation.