单项选择题
A．with support of a pad under it B．with support of a curtain round it C．with support of a pad of air D．with support of a cushion of air made by jet engines
A．be B．receive C．write D．worth
A．All living creatures die in order to be eaten by others. B．All living creatures can be the food of others. C．All living creatures decay. D．Only a small number of living creatures can avoid being eaten by others.