If the proposition No frogs are amphibians is given as false, then which of the following propositions can be immediately inferred to be true?

Some frogs are amphibians must be true once the E proposition is declared false.

The given statement No frogs are amphibians is a universal negative E.

The contradictory of an E proposition is the I proposition Some frogs are amphibians.

Contradictories always have opposite truth values, so a false E makes its I true.

This follows directly from the square of opposition.