Which units are typically included in the syntactic structure of imperative programming languages?

The correct choice highlights units specifically associated with the syntactic structure of imperative programming languages, which focus on the sequence of statements and commands. In imperative languages, execution is typically achieved through a series of instructions that change the program's state.

Conditional statements are fundamental in altering the flow of control based on certain conditions, allowing the program to execute different branches of code. Loop statements enable repetitive execution of code blocks, which is central to handling tasks that require iteration. Variable declarations are essential for defining the storage locations that will hold data and contribute to changing the program’s state throughout its execution.

This option encapsulates the core elements that govern how imperative programming operates, emphasizing the procedural aspect where the order of execution matters. The other options, while relevant to programming languages in general, include elements that may pertain to different programming paradigms rather than being specific to the syntactic structure characterized by imperative languages. For instance, options that mention functions and classes are often more associated with object-oriented or functional programming languages.