根据以下材料，回答题
Laziness is a sin, everyone knows that.We have probably all had lectures pointing out that laziness is immoral, thatit is wasteful, and that lazy people will never amount to anything in life. Butlaziness can be more harmful than that, and it is often caused by more complexreasons than simple wish to avoid work. Some people who appear to be lazy aresuffering from much more serious problems. They may be so distrustful of theirfellow workers that they are unable to join in any group task for fear ofridicule or fear of having their ideas stolen. These people who seem lazy may beparalyzed by a fear of failure that prevents fruitful work. Or other sorts offantasies (幻想)may prevent work; some people are so busy planning, sometimes planning greatdeals or fantastic achievements that they are unable to deal with whatever"lesser" work is on hand. Still other people are not avoiding work;strictly speaking, they are merely procrastinating--rescheduling their day.
Laziness can actually be helpful. Likeprocrastinators (拖延者), some people may look lazy when they are really thinking,planning, contemplating (沉思), researching. We shouldall remember that great scientific discoveries occurred by chance. Newtonwasn′t working in the orchard when the apple hit him and he devised the theoryof gravity. All of us would like to have someone "lazy" were causedby the worker′s taking time to check each step of his work and to do his jobright. And sometimes, being lazy that is, taking time off for a rest is goodfor the overworked students or executive.
Taking a rest can be particularly helpful tothe athlete who is trying too hard or the doctor who′s simply working himselfovertime too many evenings at the clinic. So be careful when you are tempted tocall someone lazy. That person may be thinking, resting, and planning his orher next book.

The author′s tone of writing the lastparagraph is ______.查看材料

A.factual
B.serious
C.satirical
D.humorous