被动语态to be与being
being 正在进行，to be将来要做
1.they insisted on the design being finished tomorrow.
a. being finished b. to be finished
为什么B是错的？
2.The children went there to watch the iron tower__
a. being ecrected b be erected
选什么？为什么?
参考答案:1,being finished, 因为insist on+doing 是固定搭配
2,being ecrected,因为是被动语态