iF in 1900 thE wAtEr usE inCountry k wAs thE sAmE As thAt inCountry x，But inCrEAsED At thE ConstAnt rAtE oF 3 Billion gAllons EvEry yEAr，thEn thE two CountriEs woulD AgAin hAvE hAD thE sAmE wAtEr usE in ApproximAtEly whAt yEAr
A、1910
B、1920 C、1930
D、1940
E、1950