我是英语师范学校毕业的,
这道题应该选择A who
这是一句典型的定语从句,关系代词who指代前面的those这个先行词,也就是后面所详细阐述的who are always ready to help others.
当定语从句先行词表示“人”时,关系代词可以用that或者who,但通常情况下都是用who,这里涉及的是一个最佳选项问题.
而通常情况下,that可以省略.
例如：English is the most difficult subject （that） you will learn during these years.