Question

more than one student作主语时，谓语动词为什么用单数

Answer 1

语法就是这么规定的：
由more than one (或more than one + 单数名词),many a + 单数名词作主语,谓语动词要用单数形式.例如：
1）More than one student has passed the examination.
2）Many a boy learns to swim before he can read.
注：如果more than后面是复数名词,则谓语动词要用复数.
more + 复名+ than one 接复数谓语.e.g.
②More students than one have been there .不止一个学生去过那儿.

Answer 2

语法就是这么规定的：
其实这个短语作主语时既有单数谓语动词，也有复数谓语动词。
单数谓语动词：“就近原则”使然。人们在说话时通常会根据最近的名词来决定谓语动词的使用；
复数谓语动词：语义使然。谓语动词的选择是根据语义的需要而定的。这种“正确”语法现象通常出现在文字表达中，而单数谓语动词搭配多出现在口头表达中。
由more than one (或more than one + 单数名词),many a + 单数名词作主语,谓语动词要用单数形式.例如：
1）More than one student has passed the examination.
2）Many a boy learns to swim before he can read.
注：如果more than后面是复数名词,则谓语动词要用复数.
more + 复名+ than one 接复数谓语.e.g.
②More students than one have been there .不止一个学生去过那儿.

More than one student was punished.
More students than one were punished.
类似以上用法的还有：
◎many a+单数名词(意为：许多)，用作主语，谓语用单数(即从形式一致考虑)
◎many+复数名词(意为：许多)，用作主语，谓语要用复数
也就是说，以上结构中名词的数决定其后动词的数。
很多小孩在那儿玩。
正：Many a child was playing there.
正：Many children were playing there.