单项选择题
Great as Newton was, many of his ideas today and are being modified by the work of scientists of our time（）
A．are to challenge B．may be challenged C．have been challenged D．are challenging
单项选择题 （）evidence that language-acquiring ability must be stimulated.
单项选择题 Jack's father suggested that Jack（）in London for a few more days.
单项选择题 I think you have talked too much; what you need now is more action and（）talk.
