Question

guarantee与promise作为保证的区别

rt，意思及使用上的区别
I guarantee you if he had survived a few more weeks on this island,you'd have figured that out.

Answer 1

guarantee 在意思上比promise 更正式。
并且语气更强一些。
在你的原句中,用guarantee 就是为了加强语气，这里如果用promise，虽然
意思上没问题，但就变大不出那种强硬，强调的感觉！

Answer 2

guarantee:
guarantee sb to do sth, 意思是担保某人做某事。
guarantee that sb do sth,意思是保证某人会去做某事。

promise:

作动词时，用promise sb to do sth 答应某人做某事
或者promise sb sth/ sb to do sth 答允某人做某事.
作名词时，用make/keep/break promise to do sth.

Answer 3

Guarantee是保证, 有实际效用.
Promise只是承诺, 可能不会实现的.