单选题 .  Everyone knows that laziness is not good. We have probably all bad lectures telling that laziness is immoral, that it is wasteful, and that lazy people will never gain anything in life. But laziness can be more harmful than that, and it is often caused by more complex reasons. Some people who appear to be lazy are suffering from much more serious problems. They may not trust their fellow workers and they are unable to join in any group task for fear of being laughed at or for fear of having their ideas stolen. These people who seem lazy may be affected by a fear of failure that prevents successful work. Some people are so busy planning great deals that they are unable to deal with "easier" work on hand. Still others are not avoiding work; strictly speaking, they are simply putting off their work.
    Laziness, however, can actually be helpful. Some people may look lazy while they are really thinking, planning and researching. We should all remember that great scientific discoveries happened by chance. Newton wasn't working on the farm when the apple hit him and he devised the theory of gravity. All of us would like to have someone "lazy" build the car we buy, particularly if that "laziness" were caused by the worker's taking time to check each step of his work and to do his job right. And sometimes, being "lazy"—that is, taking time off for a rest—is good for the overworked students or executives. Taking a rest can be particularly helpful to the sportsman who is trying too hard or the doctor who is simply working himself overtime too many evenings in the hospital. So be careful when you want to call someone lazy. That person may be thinking, resting, or planning his or her next work.1.  The main idea of this passage is that ______.