很简单的一道问题~~

There are several waysto build solid walls using just mud or clay, but the most extensively usedmethod has been the forming of bricks out of mud or clay, and, after somepreliminary air drying or sun drying, they are laid in the wall in mudmortar.

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

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

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

D.     to form the mud or clayinto bricks, and, after some preliminary air drying or sun drying, to laythem     (D)

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