as...as could be

They stood chatting together as easily and naturally as .

A it could be

B could be 

C it was 

D was 

这道题如何剖析呢?

假如撇开复杂的语法剖析，可以考虑将 as...as could be 视为习语，意思是“极其”“要……就有多……”“尽可能”。如：

The room was asquiet as could be. 房间极为安静。

Both houses wereas clean as could be. 两座房屋都极其干净。

He lay there asstill as could be. 他尽可能安静地躺在那里。

She just sat thereas pretty as could be. 她就坐在那儿，要多动人有多动人。

若是目前时态，也可以用 as...as can be。如：

John is as good acreature as can be. 约翰是一个非常好的人。

He is gentle andtame, and as clever as can be. 他非常温和也非常乖，而且极其聪明。

I can read thearticle as plain as can be. 我可以把这篇文章尽可能读了解。