单项选择题
May I speak to your manager Mr. Williams at five o'clockI'm sorry. Mr. Williams（）to a conference long before then.
A．will have gone B．mustn't follow C．couldn't have been following D．shouldn't have been following
单项选择题 I（）have gone with them, but I（）not finish my homework in time.
单项选择题 Alexander Graham Bell invented（）telephone in 1876.
