Select the most appropriate option to substitute the underlined segment in the given sentence.

The secretary to my boss is very efficient as he not only gives him the required information and also handles correspondence independently.

The correct answer is "but also handles".

Step-by-Step Explanation:

1. Analyze the sentence structure: The given sentence uses the correlative conjunction structure initiated by "not only":
"The secretary to my boss is very efficient as he not only gives him the required information and also handles correspondence independently."

2. Identify the grammatical rule: In English grammar, the correlative conjunction "not only" must always be paired with "but also" to connect two related pieces of information or coordinate clauses. Using "and also" in pair with "not only" is grammatically incorrect.

3. Evaluate the options:
- "yet also handles": Incorrect pair for "not only".
- "but also handles": Correctly completes the "not only... but also..." structure.
- "along with also handles": Incorrect grammar and structure.
- "not also handles": Redundant and grammatically incorrect.

4. Conclusion: Substituting the underlined segment with "but also handles" restores grammatical accuracy, resulting in:
"The secretary to my boss is very efficient as he not only gives him the required information but also handles correspondence independently."