l have received three letters,but _of them is from my friend, Tommy. 添all还是none
问题描述：
l have received three letters,but _of them is from my friend, Tommy. 添all还是none
答
none
首先有个but 转折 所以意思上肯定是我收到三封信，但是没有一封是我朋友tommy写的
还有all 后面应该是复数
答
none,根据语境可以知此处应该表示否定.
答
none,因为后面的谓语是is,所以不可能是all,如果是all,后面的谓语是are.而none of.后面的谓语用单数is.
翻译：我收到了三封信,但是没有一封是来自于我的朋友,Tommy.