Mark the sentences which have 'adverbs'?

(A) The machine works very well.

(B) She is a skilful worker.

(C) He seldom visits his parents.

(D) He speaks really well.

Choose the correct answer from the options given below:

The correct answer is (A), (C), (D) Only (noting that the provided option "(A), (D), (D) Only" contains a typographical error in the source material and is meant to represent statements A, C, and D).

To understand why this is correct, let's define what an adverb is and analyze each sentence step-by-step:
An adverb is a word that modifies or describes a verb, an adjective, another adverb, or an entire sentence. They often answer questions like how, when, where, how often, or to what degree.

Analysis of Sentence (A): "The machine works very well."
In this sentence, "works" is the verb. The word "well" describes how the machine works, making it an adverb. The word "very" modifies the adverb "well" (describing to what degree it works well), which makes "very" an adverb as well. Since this sentence contains adverbs, (A) is correct.

Analysis of Sentence (B): "She is a skilful worker."
In this sentence, "worker" is a noun. The word "skilful" describes the noun "worker", which makes "skilful" an adjective, not an adverb. There are no adverbs in this sentence, so (B) is incorrect.

Analysis of Sentence (C): "He seldom visits his parents."
In this sentence, "visits" is the verb. The word "seldom" describes how often he visits, which makes it an adverb of frequency. Since this sentence contains an adverb, (C) is correct.

Analysis of Sentence (D): "He speaks really well."
In this sentence, "speaks" is the verb. The word "well" describes how he speaks, making it an adverb. The word "really" modifies the adverb "well" (indicating the intensity), making "really" an adverb as well. Since this sentence contains adverbs, (D) is correct.

Therefore, sentences (A), (C), and (D) contain adverbs, which corresponds to the selected option.