Question

'Snow can sometimes threaten the lives of moutain people.'
snow- subject
can- helping verb
sometimes- adv.
threaten- action verb
of moutain people- prep.
Ms. Sue
It's all correct, but "of" is the prepostion. "Of mountain people" is the prepositional phrase modifying "lives."

christina
what do you mean by modifing lives?
Ms. Sue
The phrase is an adjective phrase that is used to describe the noun "lives."