VOA慢速英语:Testing New Ways to Recognize What Makes a Good Teacher

take part参与,参加

例句：He takes a leading part in the club.
      他在俱乐部里起主导作用。

2.They agreed to have their classes recorded on video, but only for observation by expert researchers.

only ad.只有,仅仅,只能

例句：Sap passes right through the aphides' bodies, only getting a little thicker and sweeter.
      汁液直接流过蚜虫的身体, 结果只是变得更稠、更甜。

only引导的词组或句子放在句首作状语时，通常要用倒装结构。如
Only in this way can you solve the problem.
只有通过这种方式你才能解决问题。
Only if you study hard can you pass the exam.
只有努力学习才能通过考试。
Only then did I realize my mistake.
只有那时我才意识到错了。

only to却，表示意外

例句：They reached the company out of breath only to be told they were fired.
      他们上气不接下气地赶到公司, 不料却被告知他们被开除了。

      I rushed to the door, only to discover that it was locked and barred.
      我冲到门边, 却发现门已被锁死了。

3.The report found that classrooms where students reported positive experiences were more likely to show greater learning gains.

where定语从句，修饰classrooms。

4.In many cases, administrators had been basing their comments on student test scores only.

base on使建立在…基础上,立足

例句：We must base ourselves on the interests of the people.
      我们一定要从人民的利益出发。