Final answer:
Bronfenbrenner's ecological theory has been compared to a ladder due to its multiple levels of interconnected systems.
Step-by-step explanation:
Bronfenbrenner's ecological theory has been compared to D) A ladder. This comparison is made because like a ladder, his theory consists of multiple levels or systems that interact and influence each other. Just as the rungs of a ladder are interconnected, the different systems in Bronfenbrenner's theory (such as the microsystem, mesosystem, exosystem, and macrosystem) are interconnected and impact a person's development.