有以下程序: #include <iostream.h> #include <iomanip.h> void main() double d=123.456789; cout<<setprecision(3)<<d<< , ; cout<<setprecision(4)<<d<< , ; cout<<setprecision(5)<<d<<endl; 程序执行后的输出结果是( )。
A.123,123.4,123.45
B.123,123.5,123.46
C.123,123.,123.4
D.123.456789,123.456789,123.456789