Given two variables A with value "123" and B with value 456, what will be the output of A + B in a Write Line?

When you concatenate two variables in many programming environments, the operation depends on their data types. In this case, variable A is a string containing "123", and variable B is a numeric value of 456.

When the addition operator (+) is used between a string and a number, many programming languages automatically convert the number to a string format so that both operands are strings. As a result, the numeric value 456 gets converted to "456". The two strings "123" and "456" are then concatenated, resulting in "123456".

This behavior highlights the language's type coercion feature, where it attempts to interpret the number in a format compatible with the string manipulation. Thus, in this situation, the output of A + B when displayed in a Write Line would be "123456".

The other provided choices do not represent the correct outcomes based on the concatenation operation and the types of the variables involved.