If, after extensive research, the expected observations predicted by a theory fail to materialize, then the theory is confirmed is probably false should be abandoned or modified should never be retracted

The correct answer here is that if, after extensive research, the expected observations predicted by a theory fail to materialise, then the theory should be abandoned or modified. In an instance where a theory cannot be proved, it is not confirmed and is false, so none of the other possible answers for this question are true statements.