Many studies have shown the learning-by-teaching effect.Students who spend time teaching what they've learned show better understanding and ability to remember knowledge than students who simply spend the same time re-studying.But why does teaching help？
   Researchers did a study to test their idea that teaching improves the teacher's learning because it forces the teacher to find back what they've learned.They asked 124 students to spend ten minutes studying a text with numbers on a topic which is completely new to them.They told the students they could take notes while studying，but would teach the material afterwards without notes.After studying the text，the students were divided into four groups.In one group the students spent five minutes giving a lesson on the study material without notes.The other groups either spent the same time completing arithmetic （算術(shù)） problems，teaching with a script （講稿） or writing down all they could remember from the text — a form of recalling practice.A week later，all the students took a surprise test of their knowledge and understanding of the text.
   The important finding is that the teaching-without-notes group and the recalling-practice group performed better than the group that completed arithmetic problems and the group that taught with a script.
   The researchers said the result shows that the benefits of the learning-by-teaching method are caused by recalling practice；that is，the learning by-teaching method works only when the teaching includes recalling the taught materials.
   The new findings have a practical suggestion for how the learning-by-teaching method is used in education.In order to make sure that students learn and remember an educational material，they should internalize （內(nèi)化） the material before presenting it to others，rather than depend on notes during the presentation process.

（1）Why does the author give a question in Paragraph 1？

B

B

A．To look for readers' answer.
B．To introduce the topic.
C．To keep a sense of mystery.
D．To show off his knowledge.
（2）What is Paragraph 2 mainly about？

A

A

A．How the study was done.
B．Why the study started.
C．How many people joined in the study
D．What conclusion the researchers made.
（3）What should be stressed in school education according to the author？

D

D

A．Previewing-by-teaching.
B．Note-taking.
C．Mind-mapping.
D．Learning-by-teaching.
（4）What does the text probably talk about ？

C

C

A．history textbook.
B．A detective novel.
C．A science study.
D．A guideline.