1. It is difficult to conclude what a(n) _______ student does in his spare time because every student has different interests. 2. All of a sudden, he lost his interest in engineering, and ________ his attention on learning a foreign language.3. Some of your suggestions have been ________, but others have been turned down as they are not workable.4. To make our companies __________ in the market, we have to be more creative and productive.