Which is the correct sequence used to define a local variable named "Number"?

The correct sequence to define a local variable named "Number" involves using the appropriate Appian function to create local variables. The function a!localVariables is designed specifically for defining a set of local variables within an expression.

In this case, the correct syntax includes invoking a!localVariables and passing the specific local variable as an argument. Using local!number as the argument indicates that "number" is the name of the local variable being defined. This conforms to the Appian syntax, where local variables are prefixed with "local!" to differentiate them from other variable types, such as process instance variables or record types.

The other options do not correctly utilize the Appian syntax for declaring local variables, as they either misname functions or misuse the variable declarations. Defining variables requires precise syntax to ensure that Appian correctly recognizes and processes them during the application runtime. Thus, the choice that follows the correct construction of declaring a local variable is indeed the appropriate answer.