how many students are there in your school? _the number of___the students __is__more than one thousand
说明：the number of ：.的数量后面的系词用第三人称单数的 is \was
a number of = many 许多的 修饰可数名词复数 后面的系词用 are\ were
数量只是一个数字而已,所以当成单数名词来看!