Помогите найти многофункциональность глагола to be:а) словарное значение быть

Помогите определить многофункциональность глагола to be:
а) словарное значение быть чем-то (кем-то) ; находиться где-то;
б) вспомогательн. гл. для образования Passive Voice и Continuous Tense;
в) модальное значение долженствования;
г) глагол-связка в именном составном сказуемом.

1. Because the beam (луч, пучок света) is so small, it is very important in delicate surgery and is used in eye operations. 2. Students are to be at the lecture in time. 3. Potential laser application in medicine is also being studied at the centre. 4. His task was to prepare everything for the experiment. 5. The journalist has been to his business trip in Siberia. 6. Todays generation is the best-informed than ever. 7. To be beneficial, a cadastral system should be combined with a reliable land registration system.