as dumb as an oyster

例句：

1. 1.He was so dumb that he couldn't even understand the directions on the map.
   他太愚蠢了，以至于连地图上的说明都看不懂。
2. 2. The child was so dumb that she couldn't even say her name.
   这个孩子太愚蠢了，她甚至说不出自己的名字。
3. 3. The professor was so dumb that he couldn't even answer basic questions about his subject.
   教授太愚蠢了，他甚至回答不了关于自己专业的基本问题。