1. The focus on the question was the first email in the nurture series, so bouncing multiple times likely wouldn't happen until later in the series. The form would be the best point to check for validity - and give that feedback to the user. This would ensure that good data makes it into the platform at a higher rate, and more effective than blocking freemail as this trial targets both B2B and B2C.
So B would be the preferred answer here.
2. Activity History for Interesting Moments is 25 months, Activity History for Change Data Value is 90 days. However, a text area field has a character limit high enough that it will likely never be exceeded for this purpose (65,535 total characters), and a token for a field can actually be referenced in a flow step that changes it.
So Consent History can be changed to [new string] + [old string] with [tokens or values] + {{lead.Consent History}}. For this use case, the positive and negative opt-in retention would permanently be logged in this field as the user gives and withdraws consent and it would be self contained in this field for analysis.
This is an edge case, but considering all the options in answering the question has several nuances that might be helpful on the exam.
In D, the Activity History isn't really being fully captured each time as it's being updated by the most recent activity, and then stamped onto an Interesting Moment. It's helpful, but not quite as thorough as A.
There could be other considerations in a given tech stack with other limitations - so the question is focused on "analysis within Marketo". This solution has less steps and effectively has permanent retention with each change being logged.
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