Given more attention,the trees could have grown better.中为什么不

Given more attention在这里相当一个条件壮语从句.可改写为
If it had been given more attention,the trees could have grown better.
此句是针对过去的虚拟语气,从句If it had been given more attention时态用过去完成时；主句the trees could have grown better用结构could have＋动词的过去分词．
另外,过去分词做壮语可以表被动或完成,在此表被动,the trees是动作的承受者.

主语是THE TREES当然是要用被动语态拉
HAVING GIVEN一不是被动语态,二此句话是如果加以更多细心照料,树可能会长得更好.GIVEN先更多理解为"如果",就算要用,应该也是HAVING BEEN GIVEN,但是不大用

因为这里的主语是trees啊 这里分句的given是表被动而不是表完成时.是如果能被给予更多关注的意思.

主语是trees，用被动语态