GRE Text Completion: JiJing 1373-GRE填空机经1373题 - WJ9W94K3A4EMFYU3A

Space is often referred to as the final frontier, as the only realm of which humankind has still to gain substantial understanding, yet the ocean realm is also another vast area about which our knowledge is ____________. A. erroneous B. confusing C. frustrating D. rudimentary E. delusive F. sketchy