【阅读理解】We are so used to our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted. Because we can feel that things are heavy, we think of "weight" as being a fixed quality in an object, but it is not really fixed at all. If you could take a one-pound packet of butter 4, 000 miles out from the earth, it would weigh only a quarter of a pound.
We find it hard to break free from ideas connected with living on the earth because ______.
A.it demands too great an effort for us to do so. B.we are too familiar with the way things are to question the ideas. C.we have proved that those ideas are correct. D.we are so sure of ourselves that we never doubt anything on the earth.正确答案B
