[单选题]部门活动的外部性经济的（ ）是城市产生、扩展的最主要动力之一。
A.负效果
B.合理利用
C.正面因素
D.正效果

For more than fifty years we have known, or could have known, that there is an unconsciousness to counterbalance consciousness. Medical psychology has furnished all the necessary empirical and experimental proofs of this. There is an unconscious psychic reality which demonstrably influences consciousness and behavior. All this is known, but no practical conclusions have been drawn from it. We still go on thinking and acting as before, as if we were simplex and not duplex. Accordingly, we imagine ourselves to be innocuous, reasonable and humane. 46 ) We do not think of distrusting our motives or of asking ourselves how the inner man feels about the things we do in the outside world, but actually it is frivolous, superficial, and unreasonable of us, as well as psychically unhygienic, to overlook the reaction and viewpoint of the unconscious.
47) One can regard one’s stomach or heart as unimportant or even worthy of contempt, nevertheless overeating and over