Final answer:
Communication limits apply to all programs and smart campaigns in marketing automation, not just email programs. They are important to consider for maintaining proper contact with the audience.
Step-by-step explanation:
Communication limits often apply to prevent over-contacting and spamming individuals in a marketing campaign. The correct answer to which items will communication limits apply is D. All Programs and Smart Campaigns. These limits are not just restricted to email programs but can encompass all forms of automated communication such as A/B tests, form fill outs, and any other type of program or smart campaign that sends messages or data to contacts. Therefore, marketers need to consider these limits to maintain a positive relationship with their audience and ensure compliance with communication policies.