The word ________ five letters.A. is made upB. makes up ofC. is made up of
_______ provides many hours of air for astronauts in space.
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.