13、以下语法正确的if语句是_____________ 。A.if(x>0) printf(“%f”,x) else printf(“%f”,-x);B.if(x>0) {x=x+y; printf(“%f”,x);} else printf(“%f”,-x);C.if(x>0) {x=x+y; printf(“%f”,x);}; else printf(“%f”,-x)D.if(x>0) {x=x+y; printf(“%f”,x)} else printf(“%f”,-x);