How much energy given off by the sun reaches the earth（）

A．only a very small part is available
B．the sun is too distant from the earth
C．it takes thousands of years for this energy to be stored up in coal and oil
D．our scientific knowledge is not sufficient

A．Food for astronauts must be made in a special way.
B．All meat on earth comes in bite - size pieces.
C．Astronauts will only eat cakes made from crumbs.
D．Astronauts have to go hungry in a spaceship.