The distance from the airport to the center of Sydney is______.

填空题Insulators prevent heat from being radiated into space.

单项选择题Many doctors believe that the bypass operation______.

单项选择题A．weightB．protectionC．stabilityD．power

单项选择题What does the speaker think future advertisers should do

单项选择题According to the author, we should reverse our classification of the physical sciences as hard and the social sciences as soft because______.