Correct
Not quite — the correct answer is highlighted
Show answer & explanationHide answer
Answer: (C) but hard working
Explanation
The sentence requires the use of a correlative conjunction. The standard pair for "not only" is "but also". In the given sentence, the word "too" appears at the end, which serves the same additive purpose as "also". Therefore, the underlined segment must be replaced by "but" to complete the "not only... but" construction, maintaining the grammatical balance of the sentence.