3 here !!

its refers back to the agency more clearly.
their seems ambiguous as if the animals own the stable

This eliminated all but 3 and 5 for me.

as seems awkward because it implies that the animals work is being the old hollywood system.

not unlike ties the sentence together more clearly. It says to me that the author is making a point about agencies adopting animals for parts in movies(or perhaps security) and that this is a practice that the old system did as well.

It sounds very awkward to use not unlike until I see it paired with more incorrect choices.

the animal is becoming part of a stable
the horse can't become a part of its own stable
it has to become a part of ageny's stable

eliminate 1,2,4

elimnate 3 - 'as' should compare a clause, not a noun

so, answer is 5

simplyjat wrote:Animals adopted by an agency become part of their stable, for work in the future, as the old Hollywood studio system.

1. their stable, for work in the future, as
2. their stable, for work in the future, not unlike
3. its stable, for work in the future, as
4. their stable, for work in the future, like
5. its stable, for work in the future, not unlike

OA 5

Here is how I arrived at 5

if you take the middle phrase for work in the future out the sentence becomes

Animals adopted by an agency become part of its stable, as the old Hollywood studio system.

Clearly we need like instead of as. Not unlike==like?? Some say thats correct and some say not unlike!=like. As "as" is wrong 5 remains.