6. As there is less and less coal and oil, scientists are exploring new ways of making use of   energy, such as sunlight, wind and water for power and fuel.

Trapped by the police, the terrorists made their ______ attempt to explode the bomb that they carried.

People go out with masks,________.

The study surveyed 500 families and found the main   problem people suffered was tiredness, followed by loneliness and anxiety.

What the teacher said in class set all the _____ a lot.