The sentence that contains a participle functioning as a verb is:
"The blinking sign warns drivers of a sharp curve ahead."
In this sentence, "blinking" is a present participle that describes the sign. However, it is functioning as an adjective rather than as a verb. The main verb here is "warns."
For participles functioning specifically as verbs, none of the provided sentences directly indicate a use where a participle acts as a verb. All options have participles primarily functioning as adjectives.
If you're looking for a sentence with a participle that's more verb-like, you might not find an example among these options, but the closest one would still be the sentence with "waiting," as it indicates an action being done by the students. However, the construction "are waiting" has the participle "waiting" in a continuous tense form.
Thus, while it can be tricky to pinpoint exactly what is requested based on typical grammatical definitions, the sentence "The students are waiting for the bus." includes a form of a verb in the continuous aspect.