View Compilation Error

0_0_15381608_19115.cpp: In function 'int main()':
0_0_15381608_19115.cpp:8:28: error: 'A' was not declared in this scope
    if(t>=90&&t<=100) cout<<A<<endl;
                            ^
0_0_15381608_19115.cpp:9:24: error: 'B' was not declared in this scope
   else if(t>=80) cout<<B<<endl;
                        ^
0_0_15381608_19115.cpp:10:24: error: 'C' was not declared in this scope
   else if(t>=70) cout<<C<<endl;
                        ^
0_0_15381608_19115.cpp:11:24: error: 'D' was not declared in this scope
   else if(t>=60) cout<<D<<endl;
                        ^
0_0_15381608_19115.cpp:12:30: error: 'E' was not declared in this scope
   else if(t>=0&&t<60)  cout<<E<<endl;
                              ^