Answer:
Option A
The given phrase is a participial phrase
Explanation:
Participial phrase is basically used for describing a noun. In this, words that ends with ing (present participle) or en (past participle) are used along with words that add more details to the noun. In such phrases, the noun/pronoun will act upon the recipient of the action
In this phrases present participle form is "searching", noun is "dog" and recipient of action is "survivors"
Hence, option A is correct
