Critical Reasoning

Rats are generally more active than mice. But since gerbils are generally more active than hamsters, it follows that rats are generally more active than hamsters.

Any of the following, if introduced into the argument as an additional premise, makes the argument above logically correct EXCEPT:
Gerbils are generally more active than rats.
Mice are generally more active than hamsters.
Mice are generally more active than gerbils.
Mice and gerbils are generally equally active.
Rats and gerbils are generally equally active.