The sentence that has an adjectival phrase is: His grandmother from New Zealand is visiting for two weeks.
An adjectival phrase is a group of words that describe a noun or pronoun in a sentence. It could consist of an adjective or a string of adjectives. For example, she is a beautiful, intelligent and sensible girl. In addition, an adjectival phrase not only can modify a noun but also a pronoun, like in this case, where 'from New Zealand´' is an example also of an adjectival phrase.