What we need to do is 后跟

题目

What we need to do is 后跟
"What we need to do is verify their nuclear declaration and we have put together a protocol that's based on international standards," Hill told reporters late Friday."I think there's a lot of support within the six-party process for getting this done."
系动词 is 后面似乎应该跟ing 或 to,但凭直觉似乎原型很合适.谁能解释一下这里为什么用原型?省略了to的不定式还是什么?
省略了to吗？为什么要省？语法上怎么解释？

答案

应该是省略了to ,因为do前有to,此种情况下is后的to要省略,这是一种语法现象.