Understanding the Sentence and the Substitution

The given sentence is: "He is not so a person that will betray a friend."

The underlined segment is "so a person that". We need to find the most appropriate option to replace this segment to make the sentence grammatically correct and meaningful. If no replacement is needed, we select 'No substitution'.

Analyzing the Grammatical Construction: 'So' vs. 'Such'

The words 'so' and 'such' are often used with 'that' to show cause and effect or to indicate a degree or type. However, their usage before nouns differs:

• 'So' is typically used before an adjective or adverb (or before 'many', 'much', 'few', 'little' followed by a noun) to introduce a 'that' clause showing result or degree. Example: He was so tired that he fell asleep immediately.
• 'Such' is typically used before a noun phrase (often with an article 'a/an' and sometimes an adjective) to introduce a 'that' clause showing result or kind. Example: It was such a difficult question that nobody could answer it.

In the original sentence, "so a person" places 'so' directly before the article 'a' and the noun 'person'. This construction "so + a/an + noun" is generally incorrect in standard English when introducing a result clause with 'that'. The correct structure for referring to the kind of person is usually "such + a/an + noun".

Evaluating the Options

Let's examine each provided option:

1. as a person that

   Substituting this gives: "He is not as a person that will betray a friend." The structure "not as a person that" is not a standard grammatical construction. While "not so...as" or "not as...as" are used for comparison, this specific phrasing with "a person that" doesn't fit.

2. No substitution

   This implies the original sentence "He is not so a person that will betray a friend" is correct. As discussed, "so a person that" is grammatically incorrect. Therefore, a substitution is needed.

3. such a person that

   Substituting this gives: "He is not such a person that will betray a friend." This follows the correct structure "such + a/an + noun + that" to describe the kind of person. It means he is not the type of person who would betray a friend. This sentence is grammatically sound and conveys the intended meaning.

4. so a person but

   Substituting this gives: "He is not so a person but will betray a friend." The phrase "so a person" is incorrect. Additionally, using "but" here doesn't logically connect the clauses in the intended way. 'That' is needed to introduce the relative clause describing the type of person ("that will betray a friend").

Conclusion

Based on the grammatical rules for using 'so' and 'such' with 'that', the phrase "such a person that" is the correct and standard way to express the idea that someone is not of a certain kind that would perform a specific action.

Revision Table: 'So' vs. 'Such' Summary

Additional Information: Understanding Relative Clauses

In the correct sentence, "He is not such a person that will betray a friend," the clause "that will betray a friend" functions as a relative clause modifying the noun "person". It tells us what kind of person is being referred to. The pronoun "that" here acts like a relative pronoun, similar to "who", referring back to "person". The structure "such...that" is commonly used to introduce a clause that specifies the kind or quality of the preceding noun, leading to a certain result or description.