OG12-11

nanjinshenji

OG12-11There 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
请问句子里的has been怎么理解？

DUKB24

就是一个be动词

你可以这样理解


其实和the method is ...是一样的


当你说the method has been


就是你是以现在的观点去看过去的时候被人们采用的method


时态上的变化句意有点改变


但是结构还是一样的