Could you please evaluate each of the following five sentences depending on whether it is natural or not? -- <br/><br/>(A) The professor spoke so fast that no one understood what he was saying. <br/><br/>(B) The professor spoke so fast that no one could understand what he was saying. <br/><br/>(C) The professor spoke so fast that no one knew what he was saying. <br/><br/>(D) The professor spoke too fast for anyone to understand what he was saying. <br/><br/>(E) The professor spoke too fast for anyone to know what he was saying.