Which of the following functions is used to verify whether or not an argument has been passed to a procedure?

Which of the following functions is used to verify whether or not an argument has been passed to a procedure?
A . IsNull()
B . IsEmpty()
C . IsMissing()
D . IsObject()

Answer: C

Explanation:

The IsMissing(arg) function is used to verify whether or not an argument has been passed to a procedure. If an argument is passed, the function returns false; otherwise, it returns true. The argument is a variant datatype and is optional. If the function is used without an argument, it returns true. The IsMissing(arg) function does not work on simple datatypes, such as Integer and Double.

Answer option B is incorrect. The IsEmpty(expr) function is used to verify whether or not a variable is initialized. The expr argument is a required argument and is assigned to the variant datatype. If the variable is initialized, the function returns false; otherwise, it returns true.

Answer option A is incorrect. The IsNull(expr) function is used to verify whether or not an expression contains a Null value. The expr argument is a required argument and is assigned to the variant datatype. If an expression contains Null values, the function returns true; otherwise, it returns false.

Answer option D is incorrect. The IsObject(identifier) function is used to return a Boolean value indicating whether an identifier represents an object variable.

Reference: ECDL/ICDL Exam Course Manual, Contents: "IsMissing(arg) function"

Chapter: DATABASE, ADVANCED-LEVEL

Objective: Form Design