Final answer:
The best way to combine the given sentences about Harper Lee and Truman Capote is option C, which presents the sequence of events in a clear and succinct manner.
Step-by-step explanation:
The best way to combine the sentences 'Harper Lee finished writing To Kill a Mockingbird,' 'She helped her friend Truman Capote write an article,' and 'The article evolved into his famous book In Cold Blood' is option C: 'Soon after Harper Lee finished writing To Kill a Mockingbird, she helped her friend Truman Capote write an article that later evolved into his famous book In Cold Blood.' This combination clearly and succinctly indicates the sequence of events without unnecessary repetition of phrases or conjunctions.