Which of the following cannot be checked in a switch-case statement?

The switch/case statement in the c language is defined by the language specification to use an int value, so you can not use a float value.

switch( expression )
{
    case constant-expression1:    statements 1;
    case constant-expression2:    statements 2;    
    case constant-expression3:    statements3 ;
    ...
    ...
    default : statements 4;
}

The value of the 'expression' in a switch-case statement must be an integer, char, short, long. Float and double are not allowed.