When you use a subscript value that is negative or higher than the number of elements in an array,

a$.$ execution of the program stops, and an error message is issued

b$.$ a value in a memory location that is outside the area occupied by the array will be accessed

c$.$ a value in a memory location that is outside the area occupied by the array will be accessed, but only if the value is the correct data typ

d$.$ the resulting action depends on the programming language used