Final answer:
The best combination of sentences 1 and 2 is 'I was quivering, stunned by what she said, in not knowing what she meant.', which efficiently merges the descriptions of the protagonist's emotional state.
Step-by-step explanation:
The most effective way to combine sentences 1 and 2 is option c, which states: 'I was quivering, stunned by what she said, in not knowing what she meant.' This is the best option because it combines the two actions of quivering and being stunned into a single, concise sentence without losing any of the original meaning or detail. In English grammar, using commas to separate adjectives or phrases that describe the same noun is a common and effective way to combine ideas and actions related to that noun.
The use of a comma after 'quivering' allows the word 'stunned' to act as an appositive—a noun or noun phrase that renames or describes another noun—further explaining the state of the subject. With this construction, the sentence remains smooth and avoids the choppiness that could occur with multiple independent clauses connected by commas or conjunctions.