Final answer:
The group of words 'Because of the snowfall' is a phrase because it lacks a subject and verb, making it a prepositional phrase rather than a clause. A clause must have both a subject and a verb, for example, 'It snowed more than three inches; the schools are mandated to close'.
Step-by-step explanation:
The group of words 'Because of the snowfall' is a phrase, not a clause. A clause requires both a subject and a verb, as you can see with 'It snowed more than three inches; the schools are mandated to close' - where 'it' is the subject and 'snowed' is the verb. In contrast, 'Because of the snowfall' lacks a verb and hence forms a phrase, more specifically a prepositional phrase because it begins with the preposition 'because of' and explains a reason or cause without stating who or what did the action.
For example, in the sentence, 'Nothing is as exciting as seeing a snowy owl in a winter farm field,' the word 'snowy' is used qualitatively to describe the weather and the scene. The description of 'a snowy morning' from the play captures a setting, while 'Heavy falls the snow' from the poem 'Emigrants' uses the noun 'snow' but does not include any action verb performed by a subject.