单项选择题

以下程序运行后,输出结果是 ( )
  # include<stdio.h>
  # define PT5.5
  # define S (x)PT* x * x
  main( )
   int a=1,b=2;
   printf("%4.1f\n",s(a+b));

A.49.5
B.9.5
C.22.0
D.45.0