have been to do什么用法？（OG16.SC38）

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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

correct answer：D

平行结构我可以理解，但是but后应该是一个independent sentence，那么 method做主语，has been to form 这个用法是什么意思呢，哪位可以解答一下，感激不尽！

VincentFSJ

to form和way对应，way 可以是the forming、forming、having formed吗？这几个都是状态，e的that 之后表示一件事，然而way不能是一件事

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VincentFSJ 发表于 2016-9-29 17:38
to form和way对应，way 可以是the forming、forming、having formed吗？这几个都是状态，e的that 之后表示 ...

能不能告诉我comma+but后的这个句子 主谓宾分别是什么··· 我是不太懂这个句子的成分 总觉得怪怪的···

VincentFSJ

There are several ways to build solid walls using just mud or clay, but the most extensively used method has been to form the mud or clay into bricks, and, after some preliminary air drying or sun drying, to lay them they are laid in the wall in mud mortar.（平行）