单项选择题
A．To protect the boots from water. B．To protect the soles from heat. C．To protect the floors from soles. D．To protect the boots from rubber.
A．As its gases run out, it cools down. B．It collides with other stars. C．It can only live for about a million years. D．As it gets hotter and hotter, it explodes.
A．think of money B．look at each other C．pay attention to it D．stop crossing the street