一、单句语法填空
1．Reading in bed will do harm ________ your eyes.
2．It is impossible for a cock to lay ________ (egg)．
3．(2015·浙江，16)If steel is heavier than water，why are ships able ________ (float)on the sea?
4．(2014·江西，阅读A)In his black and blue suit and with ________ oxygen tank fastened on his back，Larry dived from boats into the middle of the ocean.
