答对给财富 1.（ ）she came in,l was writing a letter A.When B.While C.since D.where

答对给财富 1.（ ）she came in,l was writing a letter A.When B.While C.since D.where
2.( )_____ you think you konw nothing,you begin to know something
A.where B.when C.before D.While
3.( )_____ there is no rain,lt's difficult to plant trees
A.where B.when C.which D.how