In response to the question posed (Contents, 30 April), how long is a piece of string? I suggest that the answer is twice the distance from the end to the centre.
Len Parkyn, Senior teacher - tertiary phase, East Sussex.
请先注册再继续
为何要注册？
- 注册是免费的，而且十分便捷
- 注册成功后，您每月可免费阅读3篇文章
- 订阅我们的邮件
已经注册或者是已订阅？
Please or to read this article.