Aresearch study that proposed to describe the behaviors of high school teachers would be
a. experimental
b. representative
c. propositional
d. descriptive

The correct answer is D. Descriptive

Explanation:

Descriptive research is a type of research that aims at showing what occurs, this means descriptive research aim at describing a specific phenomenon in the population being studied. Additionally, descriptive research focuses on finding the frequency and average of a certain phenomenon or characteristics occurring in the population studied, and are these characteristics the ones that provide a description of the phenomenon. In this way, if the research purpose is to describe the behaviors of high school teachers, it can be classified as descriptive research as the main objective is not to understand why or when, but only to describe the way teachers behave.

the answer is:

when will (v) the books (n) be (v) due?

nouns refer to people (other than pronouns), places and things, whereas verbs describe actions and are usually part of the predicate of a sentence. finally, pronouns can work as nouns and identify the participants in speech.

in the example sentence, "will" is a verb part or auxiliary verb, "be" is an infinitive verb and "books" is a plural noun.