填空题theories

单项选择题A．swim in public pools.B．give blood.C．over exert yourself.D．expose your skin to the sun.

单项选择题A．K10-15.B．K20-24.C．E10-12.D．F1-3.

填空题I

单项选择题A．at the back of the plane.B．in aisle seats.C．in window seats.D．near to the toilets.