Answer:
Water is to moisten as spade is to dig is a function analogy
Explanation:
A function analogy follows the premise of what something is used for.then in the sentence "Water is to moisten as spade is to dig" we are talking about the use of the nouns as objects or tools, water can be used to moisten if it is poured over another thing, and a spade is used to dig the soil in any kind of land. The other options describe other parts of speech or use.
