Salesforce Certified Marketing Cloud Engagement Administrator 1-10

Before importing an encrypted or compressed file into Marketing Cloud Engagement, you use the File Transfer Activity in Automation Studio to decrypt or decompress it.The official Salesforce documentation also explains that the File Transfer Activity can decrypt or decompress files located in the Marketing Cloud Engagement Enhanced FTP directory.
The Import Activity brings data into a data extension, and does not perform the decryption itself.
How to use the File Transfer Activity in Automation Studio
Move Your Data

The Marketing Cloud Engagement Setup Assistant is a guide that helps the administrator complete the initial configuration so a new account can start being used.
Its main focus is creating users and assigning roles, preparing the data structures to hold customer information, and importing data.
On the other hand, creating SMS messages and sending mobile campaigns are operational tasks in tools such as MobileConnect, and are not the core of the initial setup.
Note that Marketing Cloud is currently sometimes referred to by its product name Marketing Cloud Engagement.
Setup Assistant
User roles in Marketing Cloud Engagement

Tokenized Sending is a feature for handling contact data—such as personally identifiable information or protected health information—that is too sensitive to store in the Marketing Cloud Engagement database.
The actual data is kept in your own system, and Marketing Cloud Engagement holds only the tokenized values, referencing the necessary information via API at send time.
Field-Level Encryption protects stored data, and is not the feature that satisfies the requirement of not storing sensitive data in the cloud.
Tokenized Sending
Cross-Cloud Tokenized Sending

In Marketing Cloud Engagement, the Subscriber Key functions as the unique identifier for a subscriber in the email channel. The official documentation also explains that using the Subscriber Key lets you associate the same email address with multiple different subscriber key values.Therefore, even when a family shares an email address, you can manage them as separate subscribers per account or individual and maintain subscriber attributes and subscription statuses separately.
Contact ID is an internal identifier and is not the central element for explaining this requirement from a design standpoint.
Subscriber Key in Marketing Cloud Engagement
Key Subscriber Scenarios in Marketing Cloud Engagement

Synchronized Data Sources is a feature that syncs Salesforce CRM object data into Marketing Cloud Engagement so it can be used as data extensions.
This allows the administrator to include Sales Cloud data in a query, for example through the SQL Query Activity in Automation Studio.
Query Studio is a tool that assists with creating and running SQL, but is not the connection feature that brings in Sales Cloud data itself.
Note that Sales Cloud is still used as the name of the sales-support application on the Salesforce Platform.
Synchronized Data Sources

To send push notifications through a mobile app, you use MobilePush to create, manage, and deliver push notifications to app users.
In addition, by combining Journey Builder, you can send push notifications within a series of customer journeys tailored to customer behavior and attributes.
MobileConnect is a feature for mobile messaging such as SMS and MMS, and does not apply to sending app push notifications.
MobilePush

To route subscribers down the correct path in Journey Builder, confirm that the data referenced in the decision split is appropriate.
Journey data is a snapshot of the data captured at entry, and can be referenced consistently throughout the journey.Therefore, it is suitable for branching based on the attributes or conditions at the time of entry.
Contact data, on the other hand, references the latest values, so the two must be used appropriately depending on the requirement.
Here, confirming journey data as the data to use in the decision split is the correct answer.
Journey Data and Contact Data in Decision Splits

Enabling the IP Allowlist lets you restrict API access to Marketing Cloud Engagement to connections from pre-approved IP addresses.
This prevents API calls from unauthorized sources and reduces the risk of unauthorized access.
Field-Level Encryption encrypts stored data, the Enhanced Audit Trail reviews operation history, and Single Sign-On Authentication relates to login management—none of them restrict the API caller by IP.
Security Settings and Tools for Marketing Cloud Engagement

Publication lists are used in Marketing Cloud Engagement to manage subscription status by subscriber interest area or email type. As a result, subscribers can unsubscribe from only specific types of email rather than opting out of all email entirely.
For example, they can stop newsletters while continuing to receive important notices.
Therefore, publication lists are used as a mechanism to enable subscribers to opt down.
Publication Lists in Email Studio

Tokenized Sending is a feature that keeps sensitive contact information—such as email addresses and phone numbers—in an external system rather than storing it within Marketing Cloud Engagement.
Marketing Cloud Engagement stores only tokenized reference values, and at send time temporarily retrieves and uses the actual data from the external system.Field-Level Encryption is a feature that encrypts already-stored data, and is not suitable for the requirement of not storing email addresses or phone numbers.
Tokenized Sending
Cross-Cloud Tokenized Sending