He advises that we (should) leave early the next day.

1 这类句子中，that从句可用动词原型，也可以用should do。美式英语只用动词原型。英式英语常用should do. 但近年来受美式英语的影响，英式英语中使用动词原型有增加的趋势。需要说明的是，动词原型式虚拟语气并非省略了should, 这种说法是不严谨的，应该避免。正确的说法是，这类动词后的that从句谓语可用动词原型或should do。国内教学未区分美式或英式英语，考试中将二者同等对待。

2 另外，英国英语的非正式语体中还可以用陈述语气，关于这一点，国内英语教学并未涉及。例如：

I would strongly advise that a filtration system is added onto any pond if you wish to keep fish. 

The judge further ordered that the doctors were to be regarded as independent and to furnish copies of their reports to both Crown and defence.

And they have requested that one of their representatives will be allowed to be present in order to put their case. 

3 如上所述，英国英语非正式语体中此类that从句可用陈述语气，故当主句谓语为过去时，则可能见到that从句用would。不过作为学生，自己还是应该避免这种用法。国内考试会按错误判分。

4 在此类that从句中用shall是可能的。例句从略。但学生不宜模仿。