We (have been) good friends since we met at school.为什么用have been?

问题描述:

We (have been) good friends since we met at school.为什么用have been?
还有Why not (go) to the cinema with me?为什么用go?

1.since we met at school ----since .一般和【现在完成时】连用.动词形式是 have/has+ 过去分词
2.Why not + 动词原形 表建议,是个固定句型