What is an example of a run-time error?

A run-time error occurs when a program is syntactically correct but fails to execute properly during its run time, typically leading to unexpected behavior or program crashes. Accessing an index that is out of range of a list is a classic example of a run-time error because the program will attempt to access a location in memory that doesn't exist, which raises an exception or causes a crash.

In programming, this situation arises when you try to access elements using an index that exceeds the valid range of the list, which is defined by the number of elements within it. For instance, if a list only contains three items, trying to access the fourth item (addressed by index 3 in a zero-based index system) will lead to a failure during execution.

The other scenarios mentioned typically cause issues at compile time or logical errors but do not lead to a run-time exception in the same direct manner. For example, a missing parenthesis in a function would prevent the code from compiling correctly at all, an undefined variable would similarly raise an error before execution, and a conditional statement that is never true might lead to an undesirable outcome, but the program would still run without crashing.