To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) A function must return a value - This option is correct because a function is a named PL/SQL block that returns a value. It is designed to perform a specific task and return a value to the caller.
Option B) A procedure must return a value - This option is incorrect because a procedure is a named PL/SQL block that performs a specific task, but it does not have to return a value. Procedures are commonly used to perform actions or modify data without returning a value.
Option C) A function executes a PL/SQL statement - This option is incorrect because a function is not specifically designed to execute PL/SQL statements. It is designed to perform a specific task and return a value.
Option D) A function is invoked as part of an expression - This option is correct because a function can be invoked as part of an expression. For example, you can use a function to calculate a value and assign it to a variable or use it in a calculation.
Option E) A procedure must have a return data type specified in its declaration - This option is incorrect because a procedure does not require a return data type to be specified in its declaration. Procedures are not designed to return a value, so they do not require a return data type.
The correct answers are A and D. A function must return a value, and a function can be invoked as part of an expression.