In Visual Basic, which of the following is used for coding single-alternative and dual-alternative selection structures?

Answer: Option B

In Visual Basic, the If...Then...Else statement is used for coding single-alternative and dual-alternative selection structures.

Single-alternative selection: In this structure, a decision is made between two options - one when a certain condition is true, and potentially no action when the condition is false.
Dual-alternative selection: Here, the program chooses between two possible actions based on whether a given condition is true or false.
The If...Then...Else statement is structured as follows:

If condition Then
' Code to be executed if the condition is true
Else
' Code to be executed if the condition is false (optional)
End If

The other options listed are not directly related to selection structures in the same way:
Option A, Switch-Case block, is used for handling multiple possible values of an expression, not just single or dual alternatives.
Option C, function overloading, is a concept related to defining multiple functions with the same name but different parameter lists. It's not used for creating selection structures.
Option D, Recursion, is a technique where a function calls itself. While recursion can be used in coding solutions, it's not specifically tied to single or dual-alternative selection structures.
Therefore, the correct option is Option B: If...Then...Else statement.