Every grade in your scanf line needs to be &grade[n]
A better compiler will tell you such things.
Code:
$ gcc -Wall foo.c
foo.c: In function ‘main’:
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 2 has type ‘int’ [-Wformat=]
scanf("%d %d %d %d %d %d %d %d %d %d \n", grade[1], grade[2], grade[3],grade[4], grade[5], grade[6], grade[7], grade[8], grade[9], grade[0]);
^
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 3 has type ‘int’ [-Wformat=]
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 4 has type ‘int’ [-Wformat=]
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 5 has type ‘int’ [-Wformat=]
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 6 has type ‘int’ [-Wformat=]
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 7 has type ‘int’ [-Wformat=]
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 8 has type ‘int’ [-Wformat=]
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 9 has type ‘int’ [-Wformat=]
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 10 has type ‘int’ [-Wformat=]
foo.c:7:9: warning: format ‘%d’ expects argument of type ‘int *’, but argument 11 has type ‘int’ [-Wformat=]