PT 65 S1 Q18

Zoologist: Every domesticated large mammal species now in existence was ... ...

The zoologist’s argument requires the assumption that
(A) in spite of the difficulties encountered, at one time or another people have tried to domesticate each wild large mammal species
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Dec 2011 LSAT (PT 65): Logical Reasoning A