Three statements are given, followed by three conclusions numbered I, II and III. Assuming the statements to be true, even if they seem to be at variance with commonly known facts, decide which of the conclusions logically follow(s) from the statements.

Statements:
Some cats are dogs.
Some dogs are rats.
All rats are tigers.

Conclusions:
I. Some tigers are cats.
II. Some tigers are dogs.
III. Some rats are dogs.