Answer:
VP
Step-by-step explanation:
There is no subject, and suddenly is the verb.
To determine if a sentence fragment is a noun or verb phrase, simply see if it contains a noun or a verb. (It cannot contain both)
Whichever one it contains is what phrase it is.
NP: His lovable horse
VP: Suddenly found a dollar
NOTE: Putting the two together would result in a correct, albeit strange sentence.
His lovable horse suddenly found a dollar.
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