What is the difference between the If Then ElseIF clause and a Nested If Block? Please provide examples of how you would use each.

The "If Then ElseIf" clause and the "Nested If Block" are both used in programming to make decisions based on certain conditions. However, they differ in terms of their structure and how they are used.

1. If Then ElseIf clause:

The If Then ElseIf clause allows you to specify multiple conditions and execute different blocks of code based on those conditions. It provides a way to handle several possibilities without creating nested sections of code. Here's an example in pseudocode:

```
If condition1 Then
' Code to execute if condition1 is true
ElseIf condition2 Then
' Code to execute if condition2 is true
ElseIf condition3 Then
' Code to execute if condition3 is true
Else
' Code to execute if none of the conditions are true
End If
```

In this example, the conditions are evaluated in the specified order. If the first condition is true, the corresponding code block is executed. If not, the next condition is checked, and so on. If none of the conditions are true, the code block under the "Else" statement is executed.

2. Nested If Block:

The nested If Block involves placing an If statement inside another If statement. This is useful when you need to evaluate a series of conditions in a hierarchical manner. Here's an example in pseudocode:

```
If condition1 Then
If condition2 Then
' Code to execute if both condition1 and condition2 are true
Else
' Code to execute if condition1 is true but condition2 is false
End If
Else
' Code to execute if condition1 is false
End If
```

In this example, the code first checks for condition1. If it is true, it proceeds to check for condition2. If both conditions are true, the corresponding code block is executed. If condition1 is true but condition2 is false, the nested "Else" block is executed. If condition1 is false, the code block under the outer "Else" statement is executed.

To summarize, the If Then ElseIf clause allows you to handle multiple conditions and execute different blocks of code based on those conditions, while the nested If Block is useful for evaluating conditions in a hierarchical manner, by placing an If statement inside another If statement.