No, which is a pronoun, and can also serve as an adjective.
Which is the proper course?
He was not sure which man he had seen.
The preposition is up.
No the word every is not a preposition.
No, the word "when" is not a preposition. It is an adverb or a conjunction used to indicate time or a condition.
Yes, the word among is a preposition.
No, it is not a preposition. The word explore is a verb.
No, it is not a preposition. The word thing is a noun.
The word " I " is not a preposition, it is a pronoun.
No, it is not a preposition. The word away is an adverb.
No, the word "early" is an adverb, not a preposition. It is used to describe the timing of an action or event.
No, it is not a preposition. The word rivers is a plural noun.
No, it is not a preposition. The word has is a form of "to have" -- a verb or auxiliary verb.
No, it is not a preposition. The word surrounds is a verb form.