PT 64 S3 Q19

The conventional process for tanning leather uses largeamounts of calcium ... ...

Which one of the following is an assumption required by the argument?
(A) Leather tanned using the conventional process is not lower in quality than is leather tanned using biological catalysts.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Oct 2011 LSAT (PT 64): Logical Reasoning B