What he tried to do was to teach a male dolphin called Bass and a female called Doris to communicate with each other across a solid barrier.
出自-2012年6月听力原文
It might be tempting, therefore, to think that the old barriers have been broken down and equal opportunity achieved.
出自-2011年6月阅读原文
Now it's like a barrier has been let down.
出自-2010年6月阅读原文