Cautious IS an adjective. An adjective is an action!
The word "it" is not an adjective (it is a pronoun). A word is an adjective if it modifies (defines, characterizes) a noun or pronoun. The big tent - big is an adjective He is tall - tall is an adjective This key - this (while arguably called a determiner) is a demonstrative adjective
probable is an adjective
Hard is an adjective.
Stable is an adjective.
Studying
yes
Although used as a singular term, the typical form of some scientific disciplines employs the adjective form followed by an S. Examples : adjective linguistic / study linguistics adjective kinetic / study kinetics adjective dynamic / study dynamics
Study
adverb phrase
Christian is the proper adjective for Christ.
The prepositional phrase "in the study hall procedures" is usually an adverbial rather than an adjective phrase, because the substance of the phrase is a description of "where" something is. Example as an adverbial phrase: "A rule against loud talking can be found in the study hall procedures." A possible example as an adjective phrase: "A rule in the study hall procedures forbids loud talking."
adverb phrase
The word 'scholarly' is the adjective form for the noun scholar.The noun form for the adjective scholarly is scholarliness.
The word "hydrobiological" is an adjective. It describes something related to the study of aquatic life in freshwater environments.
SPARSEST (according to Study Island Tests)
No, "geology" is a noun, it is the study of the earth's rocks. "Geological" is the adjectival form.