Why are hydrogen bonds significant in water's properties?

Hydrogen bonds are crucial in determining many of water’s unique properties, particularly its cohesiveness and ability to moderate temperature. Water molecules possess a polar structure, where oxygen is more electronegative than hydrogen, leading to a partial negative charge at the oxygen atom and a partial positive charge at the hydrogen atoms. This polarity allows water molecules to form hydrogen bonds with one another, creating an extensive network of interactions.

The cohesiveness of water results from these hydrogen bonds, making water molecules attracted to each other. This property is observable in phenomena such as surface tension, where water can resist external force due to the cohesive nature of its molecules.

Furthermore, the hydrogen bonds significantly influence water's thermal properties. Water has a high specific heat capacity, meaning it can absorb a lot of heat with only a slight increase in temperature. This property plays an essential role in moderating the Earth's climate and enables organisms to maintain stable internal temperatures.

Thus, the significance of hydrogen bonds in water's properties lies in their contribution to both cohesiveness and temperature moderation, making option C the most accurate representation of their importance.