Understanding Superlative Degree and Sentence Rearrangement

The question asks us to rearrange the given phrases to form a grammatically correct sentence that uses the superlative degree of comparison. The phrases are: "of all the metals", "Iron", "is the", "most useful."

The superlative degree is used to compare three or more things and show which one is the best or highest in a certain quality. It typically follows the structure:

Subject + verb + the + superlative adjective/adverb + of + the group being compared

In this case, the subject is "Iron," the superlative quality is "most useful," and the group being compared is "all the metals." The verb form provided is "is the".

Analyzing the Phrases

• Iron: This is the subject of the sentence, the metal we are talking about.
• is the: This includes the verb "is" and the article "the," which is necessary before a superlative adjective.
• most useful: This is the superlative form of the adjective "useful."
• of all the metals: This phrase specifies the group that Iron is being compared to.

Constructing the Sentence

Let's combine these parts following the standard structure:

1. Start with the subject: Iron
2. Add the verb and article: is the
3. Add the superlative adjective: most useful
4. Add the phrase indicating the group comparison: of all the metals

Putting it all together, we get: Iron is the most useful of all the metals.

Evaluating the Options

Let's look at the provided options and see which one matches our constructed sentence and follows correct grammar for the superlative degree.

1. Iron of all metals is the most useful. The phrase "of all metals" is placed incorrectly here. It breaks the flow between the subject/verb and the superlative phrase.
2. Iron is the most useful of all the metals. This sentence follows the correct structure: Subject ("Iron") + verb + article ("is the") + superlative adjective ("most useful") + comparison group ("of all the metals"). This is grammatically sound and uses the superlative degree correctly.
3. Of all the metals most useful is the iron. While starting with "Of all the metals" is sometimes possible, the rest of the sentence structure ("most useful is the iron") is awkward and incorrect in standard English. The article "the" is misplaced, and the subject "Iron" should typically come earlier.
4. Iron is of all the metals the most useful. This structure is grammatically unusual and less common than option 2. While understandable, placing "of all the metals" between the verb and the superlative phrase is less standard.

Based on standard English grammar for the superlative degree, option 2 provides the most natural and correct sentence structure.

Sentence Structure with Superlatives

The sentence "Iron is the most useful of all the metals" fits this structure perfectly.

Revision Table: Key Grammar Concepts

Additional Information: Using Superlatives

Using the superlative degree correctly is important for clear communication. Here are a few more points:

• For most one-syllable adjectives and some two-syllable adjectives ending in -y, we add '-est' (e.g., tallest, happiest) instead of using 'most'. For longer adjectives, we use 'most' (e.g., most interesting, most useful).
• Irregular adjectives have unique superlative forms (e.g., good - best, bad - worst, far - farthest/furthest).
• When using 'of all', it typically comes after the superlative phrase.
• Sometimes, the group being compared is implied or introduced earlier in the text, and the 'of all...' phrase is not explicitly needed in the same sentence. However, when rearranging given phrases including 'of all the metals', it needs to be placed correctly.

Understanding these rules helps in correctly rearranging phrases and forming grammatically sound sentences with the superlative degree of comparison, like "Iron is the most useful of all the metals."