Final answer:
Instances of RuntimeException are unchecked exceptions that can occur during program execution due to programming errors. Therefore correct answer is option A.
Step-by-step explanation:
RuntimeExceptions are a type of unchecked exception. Unlike checked exceptions, unchecked exceptions do not need to be declared in a method's signature or be caught by a try-catch block. They can occur during the execution of a program and are typically caused by programming errors, such as accessing an array out of bounds or dividing a number by zero.
For example, the NumberFormatException is a subclass of RuntimeException. It occurs when you try to convert a non-numeric string into a numeric value using the Integer.parseInt() or Double.parseDouble() methods in Java.
The other options listed in the question are not unchecked exceptions. Exception, Error, and Throwable are all checked exceptions, which means they must be declared or handled by the programmer. They represent more severe issues that are beyond the control of the programmer, such as network errors, file system errors, or virtual machine issues.