Under the Copyright Act, it is permitted to use only a small portion of a copyrighted work; copying less work is more likely it is considered fair use by a judicial court.
A. copying less work is more likely
This is horrible and there is no link between likely and it, is just horrible to read. It is possible to use copying in this situation, but the other part of the sentence makes it unreadble
B. the less the work is copied, the more likely
This is the correct one. It idiomatically propose "the less X, the more Y" and likely perfectly modifies "it"
C. if it copies less work, the more likely
This does not respect the idiom proposed in B
D. when less work is copied, more is likely
Here "more" is the subject. My eyes are burning.
E. the less work copied, it is more likely such
Unidiomatical, and it is already refers to work, so the other it in the underlined portion lose its subject
So B is the correct one