I believe the answer is tense
If the underlined phrase is <em>having been warned by her mother, </em>then this is a nonessential perfect participial phrase.
Nonessential phrases are separated from the rest of the sentence by commas, and since this is a perfect participle, this is the only correct option.
<span>According to this passage, it could be said that the correct option is A (there is something royal about Sandy´s appearance because the picture was of a Queen in a diamond tiara and a high collar of pearls. It was not a picture of her grandmother, Sandy is not a queen and her name is not mentioned in this part of the story. </span>
