1. One question was uppermost in the mind of everyone in the room how had the murderer been able to escape completely unseen by the maid? A. colon B. dash C. semicolon

To determine the correct punctuation mark to use in the sentence, we need to analyze the structure of the sentence and the relationship between the clauses. The sentence is: "One question was uppermost in the mind of everyone in the room how had the murderer been able to escape completely unseen by the maid?" The main clause is "One question was uppermost in the mind of everyone in the room," and the second part is a dependent clause that explains what that question is. 1. **Colon (A)**: A colon is used to introduce a list, a quote, or an explanation. It would be appropriate if the second part were a direct explanation of the first part. 2. **Dash (B)**: A dash can be used to create emphasis or to indicate an abrupt change in thought. It can also be used to set off a summary or explanation. 3. **Semicolon (C)**: A semicolon is used to connect two independent clauses that are closely related but could stand alone as separate sentences. In this case, the second part of the sentence is not an independent clause; it is a question that explains the main thought. Therefore, the most appropriate punctuation mark to use here is a **colon**. Thus, the correct answer is: **A. colon**