as was done in

[navi tasan]

Are these sentences correct:

1-They built a great wall, as it was done in China.
2-They built a great wall, as was done in China.
3-They built a great wall, as in China.

In which case:
a-The wall was built in the same way as the one in China
and in which case:
b-the wall they built was like the one in China (but was maybe built in a different manner)
and in which:
c-The similarity between the two cases is simply that a great wall was built

Gratefully,
Navi.

 

[HanibalII]

First option sounds most natural, however none of them are incorrect.