The average amount of time students now take to complete an undergraduate degree has stretched to six years and seven months as students interrupted by work, inconvenienced by unavailable classes, or lured by one more football season find it hard to graduate.
出自-2012年6月阅读原文
About half of them are unavailable on the market.
出自-2011年12月听力原文
柯林斯高阶英汉双解学习词典释义
ADJ
弄不到的；得不到的；不方便的
When things or people are unavailable, you cannot obtain them, meet them, or talk to them.