Identify the sentences that have 'adjectival phrases':

(A) She dance skilfully.

(B) She is a skilful dancer.

(C) That was a thoughtful act.

(D) He acted thoughtfully.

Choose the correct answer from the options given below:

The correct answer is (B), (C) Only.

To understand why this option is correct, let us analyze the role of the modifiers in each of the given sentences:

Sentence (A): "She dance skilfully."
In this sentence, the word "skilfully" is an adverb that modifies the verb "dance". It describes how she dances, making it an adverbial modifier, not an adjectival phrase.

Sentence (B): "She is a skilful dancer."
Here, "skilful" is an adjective that modifies the noun "dancer". It describes the attribute of the dancer. Thus, "skilful" forms part of the noun phrase representing an adjectival modification (an adjectival descriptor).

Sentence (C): "That was a thoughtful act."
Similarly, in this sentence, the word "thoughtful" is an adjective modifying the noun "act". It attributes a characteristic to the noun, functioning as an adjectival descriptor.

Sentence (D): "He acted thoughtfully."
In this sentence, "thoughtfully" is an adverb that describes the manner in which he "acted" (a verb). Therefore, it serves an adverbial function rather than an adjectival one.

Consequently, only sentences (B) and (C) contain adjectival modifiers describing nouns, making (B), (C) Only the correct option.