Our first flag had a white elephant on it.物作主语不是不能用had吗?不是应该

Our first flag had a white elephant on it.物作主语不是不能用had吗?不是应该 Our first flag had a white elephant on it Work on it had begun before my sister left中的WORK 不是动名词作主语 要加 just had our first fight 过去完成时态=主语+had+过去分词 可是had不是助动词吗?助动词后面不是跟动词原形吗?这不是很矛盾? it做形式主语时候,一般不是不定式作真正主语吗,为什么又用动名词作主语, we had a wonderful time.had不是只用在第三人数的后面吗? 现在分词作状语时,逻辑主语不是应该与句中主语保持一致吗?为什么下面两个句中,分词主语不是句中主语呢? Our class have had a discussing recently on whether it is ne 改错Our class have had a discussing recently on whether it is a site had to be found for it 这里found不是动词吗,为什么要加be? I had a busy weekend.能用spend替换had吗?