The workers in that factory wear glasses to -- their eyes --

The workers in that factory wear glasses to __ their eyes __.A.keep;safeB.let ;safeC.let;safelyD.keep;safelyThe teacher told us that water __ about three quarters of our earth.A.covers B.coverd Cis coverd D.was coveringThe kind of trainers can make him ___ (feel)comfortable during a field trip.I think it is more impertant to do than __(say)是填say吗?完成句子：My friend ____________________ the earthquake happened.我的朋友们正在购物,就在那时地震发生了.