1. The Forbidden City in Beijing, from which the emperors ruled by heavenly mandate, was a site which a commoner or foreigner could not enter without any permission, on pain of death.

(A) which a commoner or foreigner could not enter without any permission,

(B) which a commoner or foreigner could enter without any permission only

(C) which no commoner or foreigner could enter without permission,

(D) which, without permission, neither commoner or foreigner could only enter,（C）

(E) which, to enter without permission, neither commoner or foreigner could do,

我觉得c如果连上后面的on pain of death说不通

倒是b选项 sb could do sth only on pain of death 比较好,表明不能做某事

请教大家,谢谢

on pain of death是一个固定词组，解释为：(违者)以死论处；

B的句子改变句意，意思为：仅仅在以死论处的时候，人们才可以在不被允许的情况下进入紫禁城。