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 participle describing the sign, but it is functioning as part of the noun phrase. Note that "warns" is the main verb in this sentence. However, if you are looking for a participle that is functioning as an adjective in the context of describing the sign, then that would be the correct choice.
If you're looking specifically for a participle functioning as a verb, you won't find that in the options provided, as participles are generally used as adjectives or parts of verb phrases rather than as standalone verbs.