一道选择 There are some health problems that,when ___ in time,can become bigger ones later on.
正确选项是not treated但不明白为什么not having been treated不对呢
我感觉treat和become 有时间上的关系 况且有一个later on,
还有就是they are having been done与they haven't been done意思上有区别吗、、、