— Do you know March 21st is World Sleep Day? Sleep is important to us.
— Yes. A good sleep gives us ________ and makes us happy.
truth
fame
energy
culture
We are wondering ________ we can prevent people from polluting the earth.
The gravity on Mars is only about ________ of that on Earth.
It is hard to imagine what life __________ in 100 years.
My friend John insisted that he had seen ______ alien the day before.
--- What pleasant weather! Shall we go boating on the lake? --- _______.