Scope when multiple else if are nested

Give students a grade respectively ,90 The above points are A,80 The above points are B,70 The above points are C,60 The above points are D , The following are failures .
The question is very simple. , But there are hidden conditions in it ,70 The above refers to
[70,80), The same is true in other regions .
The question is very simple. , I mainly want to talk about the scope

#include<stdio.h>
int main(void)
{
	float x,y;
	scanf("%f",&x);
	if(x>=90)
	{
		printf（"A"）;
	}
		else if（x>=80）
	{
		printf("B");
	}
	else if(x>=70)
		printf("C");
	}
	else if(x>=60)
	{
	printf("D");
	}
	else
	printf(" fail, ");
	return 0;
 }

In the middle of the else if emphasize
Many novices will write else if(x>=80&&x<=90)
This is actually wrong , carry coals to newcastle , Because it's already stay if After statement , So that means if The following statements are all related to if The content after the statement is opposite , That is to say if The following statement defaults to (x<90), Written directly else if(x>=80) that will do . When using, we should pay more attention to this aspect of grammar .

If there are mistakes, please give me more advice , Xiaobai is one .