Step 1: Understanding the Concept:
Parts of speech classify words according to their grammatical function and the role they play in the structure of a sentence.
To identify a word's class, you must determine which other word it is modifying or describing.
A word that adds detail to an action (verb), a quality (adjective), or another detail (adverb) is classified as an Adverb.
Step 2: Detailed Explanation:
Let's analyze the syntax of the provided sentence: "He spoke softly during the meeting."
1. "He": This is a pronoun serving as the subject of the sentence.
2. "spoke": This is the main action verb in the past tense.
3. "softly": This word is answering the question: "How did he speak?".
In English grammar, a word that describes the manner in which an action is performed is known as an "Adverb of Manner."
Contrast this with Adjectives: If the sentence was "He has a {soft} voice," the word "soft" would be an adjective because it describes the noun "voice."
However, in this sentence, the word "softly" is directly modifying the verb "spoke."
Most adverbs of manner are easily identifiable because they are formed by adding the suffix "-ly" to a descriptive adjective (Soft + ly = Softly).
Since "softly" defines the execution of the verb "spoke," its grammatical classification is unquestionably an Adverb.
Step 3: Final Answer:
The underlined word is an Adverb (Option D).