Which of the following statements is logically equivalent to the statement 'Some dogs are not aggressive animals'?

Some non-aggressive animals are not non-dogs carries the same content as the original O.

The given statement is the particular negative Some dogs are not aggressive animals.

Obverting gives Some dogs are non-aggressive animals, an I proposition.

Converting that I gives Some non-aggressive animals are dogs.

Obverting once more yields Some non-aggressive animals are not non-dogs, the full contrapositive.

This obvert-convert-obvert chain preserves the truth of an O proposition.