Давайте рассмотрим все времена для каждого предложения, используя времена в английском языке: Present Simple, Present Continuous, Present Perfect, Past Simple, Past Continuous, Past Perfect, Future Simple, Future Continuous и Future Perfect.
An unusual way of predicting earthquakes has been discovered by scientists in China - snakes!
- Present Perfect Passive: has been discovered
Snakes at local snake farms are being observed (by experts) to see if their behaviour changes before an earthquake.
- Present Continuous Passive: are being observed
- Present Simple: changes
Cameras are linked to a broadband Internet connection (by scientists).
- Present Simple Passive: are linked
It is believed that earthquakes from 120 km away can be sensed (by snakes), three to four days before they happen.
- Present Simple Passive: is believed
- Future Simple: can be sensed; happen
Their nests are abandoned or even walls are smashed into to escape.
- Present Simple Passive: are abandoned, are smashed
Because China is struck frequently (by earthquakes), a reliable method of predicting them must be found (by scientists) to avoid the terrible injury and loss of life that is caused (by them/earthquakes).
- Present Simple Passive: is struck
- Modal verb (must) + base form: must be found
- Present Simple Passive: is caused
Итак, вот временные формы для предложений из вашего текста. Если у вас есть дополнительные вопросы по грамматике или по другим темам экзамена, дайте знать!