Sentence Correction: Comparative Questions – Overview
The GMAT is considered by many to be ***** difficult than the TOEFL is.
The word as cannot appear with than. As is used to show similarity or equality and is usually followed by another as:
The GMAT is considered by many to be as difficult as the TOEFL is.
Than is used to show a difference, an inequality or a dissimilarity between people/things.
The correct answer is thus more.
I don't know