Why does the program skips the "else if" part?

The title says it all. My code below:

void printing(int ts1,int ts2,int ts3,float tsp1,float tsp2,float tsp3,float avg,float avg1)

{
if (avg>=90)

                 printf("\n the student got A grade\n");

else if(90<avg>=70)

             if(tsp3>90)
                  printf("\n the student got A grade\n");
            else
                  printf("the student got B grade\n");

else if(70<avg>=50&&avg1>70)

            if (avg1>70)
                  printf("\n the student got C grade\n");
            else
                  printf("\n the student got D grade\n");
else
     printf("\n the student got F grade\n");

}

Can anyone help me to spot the issue?