Final answer:
The word root referring to water is 'Hydr,' as in the word 'hydrogen' which contains this root because it is a constituent of water molecules.
Step-by-step explanation:
The word root that refers to water is Hydr. This root is found in various scientific terms related to water, such as hydrogen, which is a component of water molecules (H2O). When we analyze compound words in chemistry, the prefix "hydro-" often pertains to water or the presence of hydrogen atoms. By adding the suffix "-ic" to another element, we indicate a relationship with that element; for example, when combining with "acid", it forms compounds like hydrochloric acid. So, among the options provided, Hydr is the correct answer.