- Objective Key offers students complete, official preparation for the Cambridge English: Key (KET) and Cambridge English: Key (KET) for Schools Test. This is a revised and updated edition of Objective KET. Short units offer a variety of lively topics while providing training in exam skills and solid language development. The Workbook without answers provides opportunities for further practice of new language and exam skills either at home or in the classroom. A Workbook with answers is also available separately.