【正确答案】main() { int x,i; float y; scanf("/%d",&x); if (x<0) i=-1; else if (x>=40) i=4; else i=x/10; switch(i) { case -1: y=0; break; case 0: 【y=x 】; break; case 1: y=10; break; case 3: case 2: y=30; 【break 】; default: printf("error input/n"); } printf( "y=/%f",y);