.用适当的介、副词填空
1．You have three layers ________ skin which act ______ a barrier ________ disease，poisons and the sun’s harmful rays.
2．First aid is a very important first step ________ the treatment ________ burns.
3．You can get burned ________ a variety ________ things：hot liquids，steam，fire，radiation，the sun，electricity and chemicals.
4．Burns are called first，second，or third degree burns，depending ________ which layers ________ the skin are burned.
5．These burns are not serious and should feel better ________ a day ________ two.
6．Examples include mild sunburn and burns caused ________ touching a hot pan，stove or iron ________ a moment.
7．Remove clothing using scissors if necessary unless it is stuck ________ the burn.
8．________ second degree burns，keep cloths cool ________ putting them back ________ a basin ________ cold water，squeezing them ________ and placing them ______ the burned area over and over again ________ about an hour until the pain is not so bad.
