Thisriverformsanatural_______betweenChinaandKorea.
A、boundaryI have not heard anything from him since his _______.
With the _______of Mary, all the girl students are eager to go to the party.
Whenmakingmoderncameras,peoplebeganto_______plasticsformetal.
Sheisalready16yearsold.Butshe_______asifshewerestillalittlegirl.
The engineers in this lab spent several weeks _______their plans for the new bicycle.
