Answer: B. I am here not only to praise your work but also to commend you personally.
Explanation: Parallelism is a literary device that consists in the repetition of the grammatical structure of words or phrases in a sentence or a paragraph. Specially when we write a list of elements, we need to use the same grammatical structure. In the given sentence, the mistake in parallel structure is given by the different verbal forms in the sentence ("to praise" is in infinitive and "commending" is present participle), the option that fixes this mistake is option B: I am here not only to praise your work but also to commend you personally.
