问题：

[单选]

Research Is a State of Mind
For many years there has been much misunderstanding as to just what research is. The popular conception seems to be that there is something mysterious about it， and before any research can be done it is necessary to have expensive scientific apparatus and large， elaborately equipped laboratories. Actually， this is not so. （6） It is a simple， organized way of trying to accomplish something you wish to do—so simple that anyone can do research anywhere at any time.
First， you select the problem you would like to solve， then you list at least ten reasons why it has not been solved. （7） It takes just as much effort to solve a useless problem as a useful one. （8）
After carefully—and I want to emphasize that word “carefully”—selecting the problem and the ten things between you and the solution， you then use the same procedure as in solving a crossword puzzle.（9）In the solution of the remaining obstacles you may need some simple apparatus， but the things you will probably need most are infinite patience and persistence. Few people realize the difficulties of doing any new thing.
Maybe one of the reasons people are so easily discouraged is because of their education. During all our years at school we were examined two or three times a year. If we failed once， we were out. （10）If we are going to make progress， we must learn to fail intelligently so that we won't become discouraged at the 99.9 per cent failure.

7.（）

A . Make sure the game is worth the candle.
B . That is a step in the right direction， but I don't believe it is enough.
C . You take the easy obstacles first and by a process of elimination you eventually arrive at the one or two major ones.
D . But in selecting the problem， you need to be sure to analyze it carefully to see that it is worth the effort.
E . Research isn't a physical thing at all； it's a state of mind.
F . By contrast， all research work is 99. 9 per cent failure and， if we succeed once， we are in.