若有 int a = 1, b = 3, c = 2; float x = 1.5; 则 正确 的switch语句是
A.
switch (x) { case 1.0:printf("*\n"); case 2.0:printf("**\n"); }
B.
switch (( int )x); { case 1:printf("*\n"); case 2:printf("**\n"); }
C.
switch ( a+b ) { case 1:printf("*\n"); case 2+1:printf("**\n"); }
D.
switch ( a+b ) { case 1:printf("*\n"); case c:printf ("**\n"); }