问题
选择题
Our teachers are very friendly to us. We _____ friends since three years ago.
A. have been B. have become C. would be
答案
答案：A
题目分析：句意：我们的老师对我们非常友好，我们三年前就成为好朋友了。根据句中时间状语since three years ago（自从三年前，表时间段）可知此空应用现在完成时态，和时间段连用要用延续动作动词，故选A。