c语言百分制分等级的编程语句的菜鸟问题

#include
int main(){
float num1;
printf("Enter your mark" );
scanf("%f", &num1 );
if ( num1 > 100){
printf("INPUT ERROR:value too large!" );
}
if ( num1 < 0 ){
printf("INPUT ERROR:value too small!" );
}
if (( num1 >= 0) && ( num1 <= 34.99 )){
printf("Your score is %8.2f and your grade is F", num1 );
}
if (( num1 >= 35) && ( num1 <= 39.99 )){
printf("Your score is %8.2f and your grade is D", num1 );
}
if (( num1 >= 40) && ( num1 <=59.99 )){
printf("Your score is %8.2f and your grade is C", num1 );
}
if (( num1 >= 60) && ( num1 <= 79.99 )){
printf("Your score is %8.2f and your grade is B", num1 );
}
if (( num1 >= 80) && ( num1 <= 100 )){
printf("Your score is %8.2f and your grade is A", num1 );
}
}
用这版吧