有不有have been to do sth.的用法（OG12-11）

liujian12

 There are several ways to build solid walls using just mud or clay, but the most extensively used method has been the forming of bricks out of mud or clay, and, after some preliminary air drying or sun drying, they are laid in the wall in mud mortar.

A. the forming of bricks out of mud or clay, and, after some preliminary air drying or sun drying, they are laid

B. forming the mud or clay into bricks, and, after some preliminary air drying or sun drying, to lay them

C. having bricks formed from mud or clay, and, after some preliminary air drying or sun drying, they were laid

D. to form the mud or clay into bricks, and, after some preliminary air drying or sun drying, to lay them

E. that bricks were formed from mud or clay, which, after some preliminary air drying or sun drying, were laid

此题由于平行的原因可见选的是D，第二个分局就为：the most extensively used method has been to form the mud or clay into bricks and to lay them in the wall in mud mortar.

这里就有 have been+不定式 的用法，请问这个用法是什么意思。

liujian12

难道没有人知道吗？

hbsonlylove

method 后面省略了to build solid walls, 用不定式为了和to build solid walls 对应

liujian12

谢谢了