A standard solution of `KNO_(3)` is used to make salt bridge, because
A. velocity of `K^(+)` is greaer than that of `NO_(3)^(-)`
B. velocity of `NO_(3)^(-)` is greater than that of `K^(+)`
C. velocities of both `K^(+)` and `NO_(3)^(-)` are neraly the same
D. `KNO_(3)` is highly soluble in water