答案 (B) agreed on
agree with someone (on something)
就...与某人意见一致
agree on something 就某事达到一致意见(协议)
agree to do something 同意做某事
没有agree of这样的用法吧
原文中有一处错误,应该是two sides
Realizing that neither would win,the two sides agreed (on) a cease-fire.
翻译：
双方认识到都无法获胜,因此达成了停火协议.