Answer: The most effective way to combine sentences 11 and 12 is writing (B.) "The league produced many fine players, including Mary "Bonnie" Baker and Dorothy Kamenshek".
Explanation: B. is the correct option because this sentence combines sentences 11 and 12 in a way that it sounds natural to the reader. In other words, option B. adds clarity and helps the reader to understand the link between these two sentences. Moreover, unlike C., B. is grammatically correct and it does not contain punctuation mistakes as D. does.