Sentence Correction

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 our 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

OA is D

This is an OG problem - OG11. The explanation states that there is no need to alternate the verb phrases between active /passive. So can I have correct answers where in the first half is active voice and the second half is in passive voice. Structurally would they still be parallel. Are there any OG examples you are aware of?

Thanks
gmatrant

good question i wouldn't have noticed it was passive voice, only noticed the parallelism. but thats why i chose the right answer b/c its the only one thats really parallel