单项选择题
The chances of the physical sciences being subject to great changes are the biggest because ______.
单项选择题 The word "paradox" ( Para. 1 ) means" ______ ".
单项选择题 We know less about the astronomical universe than we do about any social system because ______.
单项选择题 The author believes that our knowledge of social systems is more secure than that of physical systems because ______.
