it has been suggested that girls avoid

来源：百度知道 编辑：UC知道 时间：2024/05/14 07:24:58
it has been suggested that girls avoid mathematics courses, not because they are difficult, but for social reasons.
请问it has been suggested 和it is suggested 有何区别？
另
It has been realized that we need air to burn anything.
It has been proposed that a meeting should be held at once.

请问这里能用it is realized ，it is proposed代替It has been realized ，It has been proposed？

主要是that后面的所要表达的内容的时态，这个时态要根据意思来定，像有些是常识性的，前面可以用一般时态，有些是经过了一段时间后才被人们承认和发现的，可以用现在完成时。
就是这点细微的差别，你说呢？

has 强调了已成事实的这样一个状态

这主要是时态的问题，
一般现在时很多时候只是表示一般经常或通常的情况，和现在无关。。
而现在完成时，是过去时的延伸，表示对现在有影响。。
而具体情况视实际而定。。