什么叫管流，定常流和临界流？

A certain good woman one day said something that hurt her best friend of many years.She____immediately and would have done anything to have taken the words back.____she said hurt the friend so much that this good woman was herself hurt____the pain she caused.____to cancel what she had done，she went to an older，wiser woman in the village，explained her situation，and asked for____.
Listening to her，the older woman___the younger woman’s distress and knew she must help her.She also knew she could never____her pain，but she could teach.She knew the____would depend only on the character of the younger woman.She said，“Tonight，take your best feather pillows and put a single feather on the doorstep of each house in the town____the sun rises.”
The young woman hurried____to prepare for her chore，even though the feather pillows were very____to her.All night long，she labored alone in the cold.Finally the sky was getting____，she placed the last feather on the steps of the last house.Just as the sun rose，she returned to____.
“Now，” said the wise woman，“Go back and____your pillows with the feather you have put on the steps.Then everything will be____it was before.”
“You know that’s____！The wind blew away each feather as fast as I placed them on the____！” The younger woman was surprised.
“That’s true，” said the older woman.“Never forget.Each of your____is like a feather in the wind.Once spoken，no amount of effort，____how heartfelt or sincere，they can never return to your mouth.Choose your words well and____them most of all in the presence of those you love.”

小题1:	A．said B．felt C．regretted D．explained

小题2:	A．That B．Which C．Who　 D．What

小题3:	A．for　 B．as C．to D．of

小题4:	A．By means 　 B．In an effort C．In addition　 D．On account

小题5:	A．question　 B．suggestion C．advice 　 D．practice

小题6:	A．sensed B．touched C．smelt　 D．breathed

小题7:	A．raise B．release C．relieve 　 D．rehearse

小题8:	A．outline　 B．outcome C．output　 D．outbreak

小题9:	A．until　 B．unless C．after D．before

小题10:

A．home　 B．south C．inside D．outdoors

小题11:

A．heavy　 B．brilliant C．colorful D．dear

小题12:

A．light 　 B．dark C．rainy D．sunny

小题13:

A．her home B．the older woman C．her bedroom　 D．the feather pillow

小题14:

A．recite　 B．rebuild C．refill D．recycle

小题15:

A．with B．just C．like　 D．as

小题16:

A．impossible 　 B．important C．imaginable　 D．immoral

小题17:

A．house　 B．doorsteps C．pillow　 D．bag

小题18:

A．action 　 B．feather C．words　 D．behavior

小题19:

A．friendless 　 B．regardless C．homeless 　 D．hopeless

小题20:

A．guarantee B．secure C．maintain　 D．guard