in his letter was his promise 的主语呢?

in his letter was his promise 的主语呢?
in his letter was his promise 的主语呢?

in his letter was his promise 的主语呢?
要我翻译的话这句话的意思应该是：这是他在信里的承诺.主语是in his letter .
但是我个人认为这句话这样说比较好：his promise was in his letter .这样的话主语是his promise .也不知道说得对不对,希望对你有用.